engine wont start

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  #1  
Old 07-19-06, 09:00 AM
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engine wont start

got this go-cart project im working on. 5hp b/s mod #130200 took the carb off and cleaned it very well [natural draft type]. new diaphram, new plug, clean gas. gets spark,getting fuel, want to turn over, and getting some back fire. but still wont start. im thinking that there isnt enough conter weight on the crankshaft. it just has a small pully for a belt thats very loose. i dont think the belt is the right size, [too much slack]. would this effect the engine from not starting? Also at times when pulling the starter cord it sometimes jerks back hard.What do you think?
 

Last edited by jarhead; 07-19-06 at 11:57 AM.
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  #2  
Old 07-19-06, 04:56 PM
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jarhead
The counter weight you are talking about will not be a problem, the flywheel will act as the counter weight that you will need. Since you say it's getting the basics (fuel and spark) I will bet you that your flywheel key is sheared causing your engine timing to be off enough to jerk the rope back every once in a while. The flywheel key is designed to shear (causing the timing to go out and not letting or making the starting of the engine difficult) A sheared flywheel key can be caused by a couple of things, stopping the motor abruptly or a loose flywheel. Check it out and while you're at it, since everything is apart, replace the ignition points too.

hope this helps.

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Old 07-20-06, 06:32 AM
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Thanks snowman, but the key is good, ill look everything over. just for the hell of it i took a compresion test, it just didnt feel like there was any or much pressure. got a reading of 35psi. not good huh?how can i increase or rectify this problem?Is there maybe something not working in sync, something stuck? I should have at least 60psi right?
 
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Old 07-20-06, 08:22 AM
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I can't tell you what the compression should be due to the fact that many of the engines have a compression release built in until the motor starts. You can do a leak down test to see if you are leaking past the rings or valves. As far as the key goes, it may not be sheared totally but if it is just a bit bent or sheared, it will throw off the timing. Check everything that is associated with it, keyway on the flywheel, proper ignition gap etc. Let me know.

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Old 07-20-06, 08:34 AM
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Originally Posted by jarhead
Thanks snowman, but the key is good, ill look everything over. just for the hell of it i took a compresion test, it just didnt feel like there was any or much pressure. got a reading of 35psi. not good huh?how can i increase or rectify this problem?Is there maybe something not working in sync, something stuck? I should have at least 60psi right?
On most small engines you want AT LEAST 90 PSI a engine will run on low compression but not that good If the engine 35 I say replace it its no good.A compression release could not be working so its not letting the engine have compression.You could check that.Also check the valves they also cause low compression.
 
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Old 07-21-06, 12:35 AM
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A common problem on thos engines is stuck valves. Often, a valve won't close all the way and causes low compression. I'd pull the head, have a look at the valves, and at the same time you can take a look at the cylinder walls to get an idea of what kind of shape the engine is in.
 
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Old 07-24-06, 05:21 AM
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took the head off to check the condition, looked good no carbon build up and the valves were in what seems to be in good shape, but found that the key was partly sheared, so im going to get another key and see if this thing wont start up. will i have to go into the engine to line up the gears for proper timing or do i just need to put the new key in and im set?thanks for the replies.
 
  #8  
Old 07-24-06, 07:41 AM
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Just put in the new key and align with the slot on the flywheel and you should be ready to go cartin. Don't start futzin with a lot of stuff untill you get it to run then adjust from there, something caused the pin to shear and there might be other issues like a bent crank or something. Have a nice day. Geo
 
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Old 07-24-06, 10:18 PM
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The flywheel key was partially sheared? Was it this way earlier when you siad it was ok, or did it happen since then? hat will definitely cause the backfire/kickback, but not low compression.
 
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Old 07-25-06, 06:44 AM
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My mistake, i hadnt taken off the flywheel, but looked and could see the key, and it looked in place. after removing the flywheel the key came out in 2 pcs. Ive replaced the key but waiting on a recoil assembly i ordered. the other was damaged during removal. since i got this project the engine hadnt run in a few years, so i dont know if the compression readings are accurate. i got the readings by hooking up the compresion gage to the engine and pulling on the rope starter to get a reading.
 
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Old 07-26-06, 08:49 PM
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Let us know how it turns out. Getting accurate compression readings on small engines can be tricky. I usually don't bother, but I've kinda got a feel for when compression is good, and when it's not when I pull on the rope. Usually, if the engine has enough compression to bounce the flywheel back when you rotate it backwards until it hits the compression stroke (quickly), then there's enough.
 
  #12  
Old 07-27-06, 05:18 AM
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Installed a new key & rebuild starter assembly, put everything together and it started right up. thanks for all the replies, it helped get this beast going.
 
  #13  
Old 07-27-06, 06:58 PM
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Good job! Glad you got it!
 
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