Motor bike wont start??

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  #1  
Old 06-13-08, 04:01 AM
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Motor bike wont start??

Hey guys i got an old kawasaki 250cc dirt bike engine. I cleaned out the carb, reset the contact breaker and now gets a good spark. I started it today to try to tune it and got it working very well. It would idle and accelerate. For some wierd reason i went to kick start it again and nothing, tried for the rest of the afternoon and nothing. So i took the spark plug out and it looked a little dry like no fuel was getting through, so i pulled apart the carb but nothings blocked! Attached it and still nothing. The spark plug still sparks so i have no idea. From an engine that was working fine to not even kicking over??? PLease help it is extremely frustrating
Thankyou,
Dominic
 
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  #2  
Old 06-13-08, 07:01 AM
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Those 250 K jobs are good ole bikes - ran hard.

First check your choke on/off. If that's OK ... Pull the plug and put about a tablespoon of gas down the plug hole. Use a half throttle and see if it will try to start. If it does the problem is in the carb/fuel delivery.

If you can't get anything, go back to your points and check them. Something may have slipped and the timing is off. You can still get a spark with an incorrect points setting = wrong timing.

Hope this helps,

Bob
 
  #3  
Old 06-13-08, 07:32 PM
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THanks for the quick reply bob,
I tried putting petrol down the plug hole but still nothing, (every now and again it might kick once but hardly). WIth the points you mention is that the point distance between the contact breaker or the timing in the engine. Im usually good with repairing the carb and stuff but never fiddled with timming. Ive also got the service manual for the bike but dont know what timing you mean?
Thankyou,
Dominic
 

Last edited by dom_inance; 06-13-08 at 09:04 PM.
  #4  
Old 06-13-08, 09:57 PM
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It would be the space you're referring to. You should have a spec for the measurement - usually in thousandths. A contact breaker point setup will normally have the gap spec to be met and a mounting plate that moves to achieve the correct timing. It's like an old style automotive setup. The point gap spec is related to coil saturation for maximum spark output. Once you deviate from that spec, however, the timing is affected.

Using the spec as a reference, moving away from it - going wider, you advance the timing. And moving away from the spec going to a smaller gap, you will retard the timing. In small engines, the point gap was a way to set the timing. As you get out of that small engine group, you would normally have a way to set the point gap (for coil saturation) and a way to set the timing (movable baseplate). In the more modern engines, all that changed with the type of ignition systems/computers, etc.

The timing spec and how to set it should be in the service manual under ignition.

What year and model do you have?
 
  #5  
Old 06-14-08, 01:11 AM
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Its a KL250A 1977 model, THe service manual seems to be a little confusing though? So to adjust the timing i only have to adjust the contact gap, cause i tried that today with no luck. The only evidence of change when the gap was altered was a change in spark strength, but still didnt start
 
  #6  
Old 06-14-08, 12:06 PM
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No, that would be odd for a bike like that. Let me see if I dig that up for you. You're getting back there in years.
 
  #7  
Old 06-14-08, 12:14 PM
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That's a pretty conventional setup, dom. You would set the point gap to spec, then rotate the base plate to set the timing.

What is your service manual giving you for the specs - point gap and timing?
 
  #8  
Old 06-14-08, 07:00 PM
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The specs the manual gives is 0.3-0.4mm (0.012 - 0.016 in) for the gap and 15 + or - 2 degrees @ 0-1600 + or - 100rpm, 35 + or - 3 degrees @ 0-3050 + or - 150 rpm for the ignition timing.
Thanks again for your help Bob i really appreciate it. Everytime i mention the year 1977 to bike shops it seems they dont even want to talk about it.
 
  #9  
Old 06-14-08, 09:19 PM
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They probably would like to have your bike and know you won't sell it.

First set your point gap with a feeler gauge. Take the heel of the points to the top of the cam that breaks your points to create the point gap and set the gap to .014. If you can tell where the base plate for the points has been setting for some time keep that location. Normally the base plate setting doesn't need very much attention. Just the point gap. But if the points aren't just about to break open or already just open at this point you'll have to adjust the timing.

If your service manual gives you definite and understandable instructions on setting the timing go by those instructions if it doesn't make any sense do this .....

Pull the spark plug (makes it turn over easier), get the rear tire up if you can (block it up or use a stand if you can), if not you can use the kick starter.

If the tire is up, put the tranny in the highest gear so you can turn the engine over with the rear tire. Hold your finger over the plug hole and turn the engine over until you feel compression. Use a straw or something similar (nothing metal) and insert it in the plug hole so it rides on the piston. Keep turning engine until the straw stops rising. At that point the engine is at TDC (top dead center).

If your manual tells you where the timing marks are located and they are readable use those for timing, if not do this to get close....

Bump your tire back in the reverse direction just enough to drop the straw about 3/8 of an inch. Now go to your mounting plate for the points and rotate the plate until the points just open. You should be in the neighborhood of 15 degrees BTC.

Now tighten everything down. With the plug out, ignition off and tranny out of gear, turn off the gas to the carb, open the choke, open the throttle fully open and kick the engine over about ten or fifteen times. This will purge any fuel from the engine.

Now go back to adding a couple of tablespoons of gas to the plug hole and, with the gas off and ignition on, choke off, and half throttle, see if it will fire.

If it tries to start, turn the fuel back on, half choke, half throttle, should go.
 
  #10  
Old 06-14-08, 09:33 PM
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Thankyou so much bob!!, this morning i actually tried to estimate the timing and gap, which got the engine started, i definately will use your scenario if the engine doesnt perform right! I tuned the air and fuel from the carb so it can get a good idle and acceleration and worked good. One thing though, i changed the oil to the right level, but the bike seems to blow alot of smoke and smells as if it is burning oil. THe oil level is well between the two marks, so i really dont understand why its blowing smoke? i noticed it also had a bit of oil residue on the tip of the exhaust, other than that the engine works pretty well and changes gears fine. Once again thankyou for your time and info bob, much appreciated!!
 
  #11  
Old 06-14-08, 09:52 PM
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dom

Make sure your crankcase breather is clear. If you keep throwing oil, plan on a tear down and a set of rings.
 
  #12  
Old 06-14-08, 10:08 PM
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i had a look a the breather passage and seems to be clear. Is there a particular way of checking if its clear, cause all i did was feed a piece of wire down and doesnt seem to be blocked
 
  #13  
Old 06-14-08, 10:13 PM
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I just tried opening the oil cap, blew down the the breather passage and air seems to be flowing fine out of the cap hole
 
  #14  
Old 06-15-08, 08:14 AM
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That's about all it needs, just so it doesn't build up pressure in the crankcase and blow oil past the rings.

I would give it a little time running it and watch the oil closely. It may have just gotten oil in the exhaust when it was tipped over sometime. If you have run it enough to get the exhaust pipe dried out and you still have the oil smoke, it could need a set of rings. There's always a chance it's coming past valve guides. Usually that oil shows up the first few minutes of running, then clears up.

If the oil level stays up pretty well, you may just want to live with it.
 
  #15  
Old 06-15-08, 06:25 PM
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Thankyou for all your help bob, i actually got this bike a couple of weeks ago, it was all run down and i decided to fix her up, ill try and post some pics on what it looks like now. Btw im from sydney australia where are you from?
 
  #16  
Old 06-15-08, 08:22 PM
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Thanks for your advertising,I like Motobike too.
 
  #17  
Old 06-16-08, 06:36 AM
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Hey bob i tried to run it for a while but still has excessive white smoke, like you said it might be the rings. Do you think that by me buying and changing the piston rings it would fix the problem?
 
  #18  
Old 06-16-08, 09:11 PM
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I found a set of rings on ebay that say they are for a kl250 but are for models 83-84. I asked the guy if they would fit the 77 model and he wasnt sure, would you guys have any idea if they would? the link is http://cgi.ebay.com.au/KAWASAKI-KL25...2em118Q2el1247
Thanks
 
  #19  
Old 07-18-08, 05:22 AM
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Bike problem after rebuild??

Hey guys, i got the rings and a gasket set for the kl250 77 model that i was fixing up. I replaced the rings, gasket and orings because the bike was giving off excessive smoke (burning oil). After i put everything back together as per the repair manual with all the correct timing marks aligned i tried kick starting the bike and all i was getting in response was a random back fire out of the carburettor every now and then, but would never actually start. The spark timing and contact breaker seem to be rightly timed. My thought is that maybe the valve timing has something to do with, but dont know how to check or fix that, so i really dont have an idea as to why its doing this extremely annoying after i have spent money and alot of time on the bike.
Any suggestions would really help and would be very much appreciated
Cheers Dom
 
  #20  
Old 07-18-08, 07:50 AM
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Still having a battle with that little gem? Overhead cam, so you would have had to have dismantled the cam chain, etc. to install the rings. You need to see how your compression is running with the valves. if you have a compression tester use that, otherwise.....pull off the contact breaker points cover so you can watch those. Then take the spark plug out. Rotate the engine until the breaker points just open.

Then use a piece of hose that will fit tightly in the plug hole (heater, water or vacuum) and blow into the combustion chamber as hard as you can. See if you can build up pressure. If not, rotate the engine 180 degrees and try again. If still nothing, your cam is out of time.
 
  #21  
Old 07-18-08, 06:09 PM
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Hey bob thanx for that reply!! I didnt have a compression tester so i did what you said. I used the hose in the plug hole, turned the engine over until the contact gap started opening with the piston at TDC. I blew into the hose and air was escaping out of the carburettor, although when i turned the engine over 180 degrees, the air built up and no escape. What do you think??
 
  #22  
Old 07-18-08, 07:05 PM
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Sounds like your points are firing on an open intake = not good = backfiring. If your cam rider (for the points) was on the heel (low part of the point cam) when you got the pressure with the piston at TDC compression (you have pressure) you're off 180 degrees - roughly. It could be a few degrees either way, but in fixing it, will have to be zeroed in exactly. What did the points look like when you had the pressure build up?

There are some engine designs with valve overlap, not only of themselves, but into the next stroke = performance things. But you shouldn't have the points breaking with the intake open.
 
  #23  
Old 07-19-08, 08:47 AM
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I had a look and when there is pressure the points are closed, but when i turn the engine over 180 degrees where the air escapes out of the intake the points are starting to open, which is obviously not right. Do you know how i could go about fixing it bob?
 
  #24  
Old 07-20-08, 02:45 PM
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The cam issue is pretty easy to check and fix... if you have the alignments marks/method to work with. Usually it's a mark on the cam gear and one on the crank gear - align those and everything works. Yours could be that setup or a variation of it. I'll see if I can find how that engine is aligned.

The ignition we can work around and get exact to specs based on the stroke. With the cam, though, one tooth off, could be as much as 10 degrees off for every tooth you're off on a 36 tooth gear. The cam timing will have to be exact.

Will post back.
 
  #25  
Old 07-20-08, 09:24 PM
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We're going to need a service manual on that one. There is a specific procedure to getting it set. If you have a service manual (which is a pretty good investment for the money) it should be in there.
 
  #26  
Old 07-21-08, 12:48 AM
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Yeah bob ive got the service manual and have done everything it says to do in relation to lining up the cam saft sprocket and the crankshaft sprocket. The camshaft sprocket has a kl250 mark which lines up with a ridge cast into the underside of the camshaft housing which acts an index mark. In relation to the crankshaft sprocket there is a T mark which aligns with the outer cover mark. Ive lined these up serveral times to make sure, with the piston being at TDC, but even though they line up i still get the same problem, only a random back fire out the carby but never starts?????
 
  #27  
Old 07-21-08, 07:46 AM
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Hey bob, i got the bike to kick over tonight! hip hip horay, i reset the timing marks again and fiddled with the ignition timing until i got it right. It started twice so tomorrow i will tune it properly and ill keep you updated, ill also sent you some before and after pics when its done. Thanks for your help Bob!!
 
  #28  
Old 07-22-08, 12:02 AM
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hey bob, i think i jinxt it last night. I tried it today and it started to kick over but sometimes would kick back the kick lever which meant that the timing was over advanced so i fiddled with it to the books standard but not much response sometimes it would kick over once but nothing much. I examined the points and they look worn down a fair bit, even though there is still spark could worn down points be the problem?? because ive continuously (all day) been fiddling around with the ignition timing with not very good results, ive tried different gaps, used the filler gauge, tried turning the baseplate and used your scenario that you posted earlier. This bike is really becoming a pain, ive spent so much time on it trying to adjust it. Yeah so if you think that renewing the points might make the difference tell me so i could try and get my hands on a new set. Thankyou
 
  #29  
Old 07-22-08, 10:25 PM
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dom:

As a rule in terms of the ignition settings, just do it once, check it , then leave it alone. It's usually something else.

First check something and make sure it's free, clean and lubed. Pull the base plate for the points off the bike and check the cam and the mechanism behind the cam to make sure it moves freely. Then reassemble.

In terms of your points, check them to make sure they mate flat against each other and are clear of pitting. If they are smooth, set the gap with a feeler gauge, clean them with acetone or a clean dollar bill, then leave those alone. The points are as good as they are going to get.

Then set the timing, tighten the base plate and don't do anything else to that.

If you've got the timing marks lined up for the cam/valve timing, check that and leave that alone.

Now see if it starts or if you still have a problem.

At this point you have to move on to other potential problems.
 
  #30  
Old 07-23-08, 05:33 AM
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I cant believe it bob! i thought about it and it came to me... I realised why the timing plate wasnt lining up with my original marks. I found out when i reassembled the ATU i put the heel sleeve on the other way, originally the heel pointed toward the left and i put it on so the heel was facing the right. I took it off and put it back to the original position, adjusted the the gap and it started first kick. I cant believe it something so small made the difference. Once again thankyou for all your time and help and i will post some pics when im done, thankyou bob!!
 
  #31  
Old 07-23-08, 09:14 PM
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Now that is good news!!!! I suspect you've added a lot to your moto-mechanicing skills.

One last piece of advice... keep the wheels pointing down

Take care, stay safe
 
  #32  
Old 07-30-08, 11:39 PM
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Hey bob,
i bet your sick of me asking stuff but as you know i got the bike going. I got a bit of an issue with its performance though. Without an air filter (ive got a uni filter for it) the bike runs well, idles and accelerates, ive used the mixture screw to acheive a good result, although it was never perfect, as it struggles a little after you ride it, but when i put the air filter on, the bike struggles alot, no mater where the mixture screw is. It seems to deprive the bike of oxygen and chokes it, making the bike stumble alot during acceleration and the odd the backfire. Ive had a look at the spark plug and there is a film of black carbon, which to me shows its burning too rich, so i decided to buy a 2 grade hotter plug to see if there is a difference, but didnt make any difference. I know for a fact that the carb is clean i cant count how many times ive soaked it and cleaned it making sure all the passage ways (pilot and main jet) are clean. The float and needle is fine with no signs of wear. So i dont know what to do, ive fiddled with it for a couple of days now with never a perfect result?
Help would be much appreciated, thanks!
 
  #33  
Old 07-31-08, 06:42 AM
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No problem with the questions. Glad to hear from you.

You have a few possibilities = weak spark, late ignition timing, or rich carb input.

The ignition timing can be checked, which I believe you have a good handle on now. You can recheck that, but don't set and reset the points if you have those in good shape. Use a new plug to check the spark and make sure it's grounded to the engine. The spark is OK if you can visibly see a blue spark. Usually it's easier to see in a darkened garage.

That point setup should have a condenser in the ignition system. Does your manual show one of those? If you have a bad one it can rob the ignition of energy = poor spark or no spark. Normally they aren't too expensive.

If you have a weak yellow spark, think about replacing the coil, but I would change the plug wire first.

The engine should have an auto advance, usually right behind the point mounting plate. It would have to be able to move the point cam = advance and return to the set position. If not it may be stuck = late ignition timing as the engine speed increases.

If you clear the ignition hurdles ( really doesn't take too long), you need to take a look at the carb. First make sure your air flow path (intake and exhaust) is clear. Then check your choke to make sure it will set in the fully off position.

After you have your bike warmed up. Pull the air filter, for now ( make sure it isn't dusty around the engine = common sense). Start it up and crack the throttle (snap it open and closed) it should rev right up. If not go to your metering screw and turn it in until the engine snaps up in rpms pretty well. Now count the turns of the screw to fully seated. If you're around 1 to 1 1/2 turns you're in pretty good shape. If you get all the way seated without affecting anything you may be getting gas past the float valve or the float may be bad.

If so, take the float and submerge it in gasoline for about an hour. If it's a brass type, pull it out and shake it to see if you have anything in it. If there's any liquid at all, replace it. If it's fiber it should float by itself with about 1/3 of the float above the gasoline. If not replace it.

A float valve can look fine, but when the vibration of engine hits it - especially with a single, it lets fuel past = overly rich condition. Sometimes you can seat a brass on brass float valve by putting whiting toothpaste on it and hand spinning it back and forth in the seat. If it's a neoprene tipped job it'll have to be replaced, but they aren't expensive.

That will move you ahead. I'm sure it's a simple fix, but some of those things take time. When you get it in good shape, you probably won't have to work on it again for some time.

Keep us posted,

Later.
 
  #34  
Old 07-31-08, 11:55 PM
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Hey bob,
I had a look at the timing and spark and all is good. The spark plug has a perfect strong blue spark. I pulled apart the carb, removed the fibre float and submerged in gasoline and did not sink and floated to your specifications (1/3 out). I put it all back together, started the bike, and rode it without hassel. The bike revs and idles fine. But... when i put the air filter on i get the same problem with the bike choking/hesitating on acceleration. Still puzzeled??
 
  #35  
Old 08-01-08, 12:19 AM
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is there gas in the carb? if none check the fitting where the fuel line goes into it. that could be blocked. or the fuel line could be blocked. past that i cant think of any thing else right now
sorry if i wasnt any help
 
  #36  
Old 08-01-08, 05:07 AM
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dom:

If everything is working fine without the filter it must be adding enough resistance to the air flow to drive the fuel/air over the limits.

An intake starts essentially as unrestricted airflow through an engine. Then you add the complication of the combustion = a bulge in it that is accelerated by porting it out the exhaust and by blocking the intake with the exhaust open. The more air flow acceleration = better intake = better performance. Everything is drawn up from the carb by restrictions = venturi, which accelerates the flow at a given point leaving an atmospheric pressure drop at a point in the carb = vacuum = drawing power for the gas from the carb. The configuration of that venturi in a slide carb like you have is usually done with the cutaway of the lower end of the throttle slide. All that stuff is calculated and shaped by the white shirt guys at Kawasaki, Inc. Along with those calcs is a restriction imposed by the filter which is practically nothing. But, anything above that practically nothing, like a dirty filter or a high resistance filter = too much vacuum at the carb jet feed into the air stream = rich condition.

The difference between the resistance an air filter imposes on the system as opposed to the venturi is the air filter puts a vacuum on the choke circuit. The venturi devices pull through the running circuit of the main jet.

As you move away from the ideal fuel/air mixture of about 18:1 to an overly rich condition (this is with a fully functional ignition) you'll see a small increase in power with slightly better internal cooling, then less power with poor acceleration, then bogging down and flooding out.

Once you clear the ignition system from malfunction you can look at the carb. Aside from leakage, you have the metering configurations (jet size/throttle) and the level of the fuel in the float bowl. Jet size in an OEM configuration normally isn't suspect. It can be and may have been modified = too rich now. The needle position on the slide of the throttle may have been moved up = too rich. Or the fuel level in the carb may be too high = rich condition.

The metering screw you have been setting will control the fuel flow within a small range inside the much larger range of the just mentioned settings.

Once you have any broken parts taken out of the equation, you have to start looking on the settings of things that affect the fuel flow into the airstream.

You have a quite a bit of room to work where an air filter out the box is concerned. I really doubt if the problem is the air filter. But you are probably at a threshold of an overly rich mixture in the carb (setting, etc.) and the small amount of resistance the filter is putting on the air stream is driving the fuel/air mixture over = too rich = your problem.

Don't discard your filter. If your float and float valve are fine, I would pull the throttle out the top of the carb. Under the spring you'll see the slide and in the center of the slide you should have a metering needle positioned by a clip. Note the groove where the clip is located and move it up one groove (toward the top or short end of the needle), reassemble and see how that works.

I suspect someone has made some attempts at performance tuning on the bike and sent too far with fuel/air mixture.

Sorry to write a book for you - the subject has a number of possibilities.
 

Last edited by marbobj; 08-01-08 at 07:57 AM.
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