Engine I.D.

Thanks in advance for any advice! I purchased a Craftsman Model 917.257470
,38" inch cut mower. I bought it as a fixer uper. I received the manual with it and it states that it has a Briggs 12hp (281707) engine. However, the engine that is mounted is not a briggs. On the fly wheel housing it has a decal that says Craftsman, OHV 12hp.,, I think it is a Tecumsah but just not sure. Here is the numbers from the front of the fly wheel housing:

143 386012 ser7863D

Can someone ID this engine by the number and where can I find the service manual?

Thanks bunches for your help!
Dave237

 

You are right, it is a Tecumseh engine. I can't remember the exact address, but you can view tecumseh manuals at a site named CPDonline.com or something similar. Try CPDmanuals or CPDonline in a search engine,

 

Cheese,

I have found the service manual at CPD. Please, let me know if you or someone else ever needs the link to obtain these manuals. Thank you so very much for all your help. I have learned so much from you and others on this forum. Another question.......

Do you know how I can translate my Craftsman engine to the eqiv, of the Tecumseh's engines. My engine does not have the standard tecumseh numbers. I would prefer to do business directly with the source if possible. Also,

I have turned this engine over (won't fire up) (got to do some more testing with spark and gas flow) and it seems as if the compression is stoping the piston travel for just a milli second (see some piston bounce back) then it will roll over slowly until the next compression stroke. It could be just a lose connection to the starter but I have read, on this forum about some type of compression release mech. on the cam. Could this cause this problem or could I be barking up the wrong tree to early in the game ?

Thanks again and God Bless
Dave

 

Most likely it just needs the valves adjusted.

If you need parts for the engine, the sears #s are actual tecumseh #s. You should be able to view a parts list and breakdown at www3.sears.com. Type in the engine model# and click view diagram or view parts list.

I don't have an exact cross reference for your engine #, but it sounds like a OHV120.

 

Thanks Cheese. I do appreciate all your help.

God Bless.
Dave

 

That "143" number crosses to a Tecumseh OVM120-200020B. The 7863D is a bit puzzling in that the 863 of such indicates the day of the year it was manufactured and since there are only 365 days in a year, i'm going to guess that is actually 7363D and therefore would be a year 7 day 363. You have to guess the decade to go along with the year. But based on the Tecumseh model #, i'd say it is a 1987 which would make it a 1988 model year unit.

 

puey61,

Thank you so very much for the info. Without your help us guy's would be in the dark. You are correct.... I read the ser# wrong. It is indeed 363 not 863. I was slightly puzzled over the same issue.

I'm going to need a carb rebuild kit. The sears web site does not list a complete kit... only the individual parts in the kit. Do you have the correct Tecumseh part number for this kit. The best info I can supply for the carb is as follows:

Sereis 4 style. Number on the carb is : 1282 M7T. It has a tygon tube in front of the throttle plate. It does have an idle mixerture screw.The bowel is secured with a brass bolt (no high speed adust).

I will need a full rebuild kit including any bushings for the choke shaft. This one is worn badly.

Thanks again for all your help.

God Bless
Dave

 

If in fact the carb ID# you provided is correct, this is not the original carburetor for this particular engine. The original carb should be adjustable. Nonetheless, using the carb # you supplied, use the following: 632760B, kit (this is a fits-all for Tecumseh and there will be several unused parts from the kit but is still relatively inexpensive and will have everything you need); 632470, bowl nut/main jet; 632472, choke shaft. There are no replaceable bushings for either the choke or throttle shafts, replace such if worn.

 

puey61,

Thanks again for your help. I will be ordering this kit soon. Any ideas on where to get it from?, being Tecumseh does not deal direct with the public unlike briggs.

After, this evening removing and cleaning throughly, the carb, I did do a check of the carb numbers and found them as correct per my last post. The carb may have been replaced at some point in it's life or the engine ID is wrong. It is a verticle shaft 12 hp OHV engine and the manufacture date is indeed 1987 363rd day as you suggested.

After a valve adjustment, (I hate those hollow nuts on the rocker arm post which refuse to stay where you put them and I know will have to be replaced, any ideas ?????), per Cheese's advice, (thank you sir) and despite the worn shafts in the choke and throttle post, SHE sprang to life after a long rest. I have some oil leaks around the valve cover but she's wanting to run.

Do you have any suggestions corcerning either the parts ording, rocker arm nuts or valve cover leaks?

Thanks again for all of you guy's help!
God Bless,
Dave237

 

I think that engine has the O-rings on the push rod tubes. That's a leaky engine and head removal is required to replace these o rings if equipped. There are also gaskets at the valve cover bolts and the valve cover itself. There is a gasket set that includes all these. I can get the # if you need it.

 

Purchase parts through either a local Tecumseh dealer or you can go to Sears Website and order them - you'll just end up paying as much for shipping as you will for the parts that way.

 

Cheese and Puey61,

Thank you both very much for all your help and advice. I will keep everyone updated when I finish with this engine which may take some time yet. Cheese, you are very correct. This engine pumps so much oil out of the valve cover and head area that I'm thinking of starting my own oil company...

Yes, I would apprecaite those numbers for the gasket and o-ring set Just to make sure I'm accurate.

35331b gasket set
35332 O-ring set
Are these numbers correct for an ovm120 1987 model ?

I had planned on pulling the head anyway just to inspect the piston, cylinder and valves and for a good cleaning so I will replace all these parts at that time.

Besides the inner workings of the valve / head being overly busy are there any precautions I should be aware of when I tear down / rebuild the head /vavles?

Thanks again and God Bless!

Sincerely,
Dave

 

Yes, the # 35331 B is the correct #. This should be all you need, it comes with the Orings too.

 

Thanks Cheese. They're on order and I will let you know how it goes.

God Bless,
Dave

 

Cheese,

Thanks again for all your help. (ref (OVM-120) I did obtain the gasket and O-ring kit. I did a tear down and cleaning. Piston, Cylinder,Valve faces and seats, push rods, rocker arms and their bearings look like new. Very little wear to the eye and fingers.

After, installing all new parts and closeing it up she fires fine and runs well. No oil leaks however, It is burning oil to the tune of 1 mile of smoke per 4 piston strokes. I'm puzzeled and here is why:

The cylinder (no scores and very smooth) and piston are in very good condition. I have great compression...So, I'm assuming the oil is not coming in from that direction. I did note a major build up of thick heavy carbon in the head next to the intake vavle which I take as a clue however, I would assume the new o-ring that was installed on the intake valve stem would have stoped this leak into the head. But, looking back, I did notice a lot of woble in the valve guides when I placed them in the head without the rocker pan attached. I would guess about .030

This engine will fire up and run clean for about the first 30 seconds when cold. After this, it will begin to blow excessive blue smoke. It will then take spells and run pefectly clean (no smoke) then begin smoking again but with no change in engine performance. It does smoke worse when the mower is climbing an encline again, with no change in engine performance. Oil level is normal!

I'm thinking a needed valve job is called for. Any opioins? If you agree, how would you suggest I proceed?

Thanks again and God Bless,
Dave

 

My word, .030" is a LOT of play in a valve guide! I doubt it would hardly run, if at all with that kind of wear. It would definitely smoke a lot. By your description, I would say your crankcase breather valve is causing your problems, but it could also be valve guide wear, or a combination of both. Could the oil level be too high?

 

The valve guide kit is part number 730218, which contains two guides and the breather part number is 28423.

 

Cheese, oil level (straight 30) is on the money or slightly low. I may have went a bit over board with .030 of play however, I was machinist for 6 years and I know that it was at least .010 which I know is still excessive.

After posting last evening I considered the breather as a possible cause. I seem to remember the reed not being fully closed when I cleaned and remounted it. I will try a new one first. If this does not fix the problem I'll go with new guides.

Question:
I will mic the valve stems for wear and out of round. At what point should I reject the valves? Also, I have read about a hot oil bath (ouch) and arbor press for removing these guides which I don't have. Can I accomplish the install without all the above. Any suggestions please?

Thanks Puey for the part #s and thank you both for your knowledge but most of all,,, Thank you for your time!

Sincerely and God Bless,
Dave

 

Guys,

I did replace the breather, thanks for the part number Puey. It has cut the smoke 3/4's! It is almost perfect however, there is still some smoking which I just can't get used to. I will need new valve guides, no doubt. Again, as in my post above, I need some valve guide recommendations...(OVM 120)!

I have read about a hot (400 degree) oil bath (ouch) and arbor press for removing these guides which the press and GreeLee cuters for the valve faces, I don't have and the cost of such is just not worth it. Can I accomplish the guide install without the above. Any suggestions, please?

Sincerely and God Bless,
Dave

 

If you found this manual at cpd online, http://www.cpdonline.com/692509.pdf
It should have complete service and overhaul instructions. If machine work is needed that u are not equiped for, I would suggest letting a shop do it that is...most I have checked with would do it for an hour labor.

 

Azis,

Thanks. Yes I do have that manual and I think I'll follow your advice. I'll let someone thats equiped do this job.

Thanks again and God Bless,
Dave

 

I agree, many automotive machine shops would be equipped to do the repair. Since you're getting this far into it, I would also replace the rings at least. If they are worn, the oil ring will allow the engine to smoke. If it has enough time on it to have worn out the valve guides, then it needs rings almost for sure.

 

Cheese,

Thanks for the advice. I mowed with the mower today and it did a great job. The smoke is not that bad however, it does puff out a bit here and there. I think I'll wait a bit before I tear back in and do just what you suggest. When I do open the crank case and remove the bearing cap for the ring replacement, can I just replace the caps and bearings "as is" as long as they're OK!

Thanks again for you guy's help and advice.

God Bless
Dave237

 

Yep, as long as they're ok. Don't forget to hone the cylinder when replacing the rings and cut the ridge at the top of the cylinder if it has one worn into it.

 

Thanks again. When I get the time I'll have a go at it. I'll be sure to follow your adivce when I replace the rings. Alll the help is greatly appreciated!

God Bless,
Dave237

 

Cheese,

Got down to doing it.!

I have seated new valve guides per Tecumseh instructions, (hot oil bath), removed guides, and reseated new ones. Borrowed a friends "Neway Valve cutter set" and re-cut valve seats. Original valve stems and faces are within specs.

Everything is going well! I have rebuilit carb however, Puey61 had given a total carb rebuild kit #"for an all Tecumseh carb rebuild "(632760B) in a previuos post. This number is accurate for all welch plugs and carb o-rings however, it is minus the the choke and throttle shafts, main jet bolt, and idle jet screw as I thought, he had suggested. Please, forgive me Puey' if I have miss read your post, suggestion or number? I ordered the shafts and springs as individual parts however, at Tecumseh's great profit margin!

Now, Im down to the cylinder bore! Cheese, I need your great advice hear???


This engine has great compression, seriously, it does! There is vertical wear from sand ingestion and the ring gap measures .015 with the standard rings. Let me know if I’m wrong here: ?

I want to hone the bore with ( 380 grit stones ) until I obtain a good scored bore that has a well defined cross hatch. After which, I have not removed that much metal! I will re-ring with standard rings.

Should this produce a non oil burning engine ? Please, advise with any advice?


God Bless, Dave237

 

Sounds like you've got a good game plan. I will say, don't overdo the honing. You don't have to make the cylinder look like it is freshly machined. You want to cut the glaze from the cylinder and smooth up any scores and take them out or close to out if you can without honing too much. Get a good enough crosshatch pattern to allow cylinder lubrication and good ring/cylinder seating. You probably won't go too much, but check once in awhile to make sure you're not getting too much metal removed. If you get the scratches out or close to it, cut the ridge at the top of the cylinder if it has one, and get a fair amount of crosshatch pattern over the entire cylinder wall surface, you should be smoke-free and good to go as long as the ring end gaps check out ok. Don't use chrome rings. Just use standards.

Oh, and wash the honed cylinder out well after honing. Spray brake cleaner or carb cleaner works well. Keep the honing stones oiled.

 

Thanks for your advice cheese!

I will follow your advice. I'll let you know the results when I can finish it up.

God Bless,
Dave237

 

Cheese,

Project completed! I did lightly hone and installed new rings. I scored light scratches in the crank,cam and balence gearing to make certainly sure it was put back together in time. She runs great! No smoke....! A new lease on life for this old engine! After all the work and effort, I guess it was worth it; just to hear it run like new again! "Very addictive indeed"! I spent less than $150.00 for parts and special tools;total. Now, I have another grass demon that will give me many hours of mowing bliss...!

Tuning it up now..! A couple questions please....?

(1). Why will a "lean" mixture overheat the engine? I assume it's due to a to (complete), "thorugh" burning of the mixture. Is this correct?

(2). Cheese, why did you suggest not using chrome rings for a rebuild in your last post?

Thank you all for your help and replies!

God Bless,
Dave

 

Great! Good job

You're pretty much accurate about the heat and lean condition. Another contributor to the heat is the fact that the engine is not producing the required power needed to do the job, and the air fuel mixture is completing the burn before the piston is pushed to the bottom of it's stroke.

I don't reccomend using chrome rings on engines with steel/cast iron bores. The reason is because the chrome is so hard, it will take forever to seat in (if it ever does). Sometimes using chrome rings in a sleeved engine will result in more oil burning than it had before the rebuild. On an aluminum cylinder, however, chrome rings are the way to go. The chrome rings will actually seat the cylinder to them, instead of the rings and cylinder seating together.

 

Thanks for the info Cheese. I have learned just enough from you and the rest of the crowed to be dangerous when around gasoline and small engines... LOL!

This project would not have been possible without you and all the rest whom gave of their time and advice. All the help is very appreciated!!!!

God Bless and Sincerely,
Dave237

 

Won't this cause shaving. Or are they big enough to matter?

 

Not really shaving, but yes, it causes tiny microscopic metal particles to wear off into the engine. This happens no matter what method you use, chrome or steel rings. They have to seat, and the only way for them to seat is to wear into each other. This is why you should change the oil after an engine has broken in sufficiently.