Help with a super rich condition.

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#1
I purchased a 91 CR 125 last spring that was in terrible condition. I tore the bike completely down to the frame and rebuilt it. I replaced the exhaust with an fmf fatty and fmf spark arrestor muffler. I rebuilt the top end and had the cylindar resleaved. I cleaned out the carberator and restored it to stock settings.
I mixed my gas a 40:1 and was burning up spark plugs every two hours. I leaned out the clip and that helped out some but I was still burning up plugs. So I went down two sizes on the main and one on the pilot (which happened to be the suggestion from FMF) and that was a little too lean on the top so I move the clip one position richer and it was running great, like a new bike. That was two weekends ago, this last weekend I went riding it started fine and ran great for about an hour then I stopped and talked to some guys at the track and when I was done I couldn't get it to start. (even when it's cold it would start on two kicks) I was able to bump start it but it ran terrible. I went back to my car and took out the plug and it was by far the worst fouling I had ever seen. There was also more black gunk out of the muffler then ever before. Worse yet there was black stuff seaping out of the head gasket. (seaping out in only one spot about two inches across) So here's my question is the head gasket alone enough to make it that rich or is there something else. I looked at the carberator and both of the jets were still there. Any help would be appreciated, I hate taking my bike to the local shop unless its to get a tire changed.
 
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#3
Super Rich 1991 CR125

I will check tomorrow and see what the level is. It's hard to tell the level though with out a dipstick. I know there is the screw you remove that tells you when you've reached the desired level when changing the oil, but if it's below that it's hard to say exactly how far below it is. Is changing the crank seals very difficult. As stated I can take the bike apart and I can take just about anything apart, it's the getting it back together that sometimes causes the problems. I have a clymer manual but sometimes that book just doesn't cut it. How is the crank lubricated on a two stroke? Is it the premix or is it the trans oil?
 
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zoommx

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#5
hmmm. fix the head gasket first. Coolant in the combustion chamber will cause problems. Don't know about it being 'black', but maybe, especially after mixing with gas/oil and igniting. Replacing the crank seal IS a complex job, got to split the cases. It is time consuming and takes alot of attention to detail and if you aren't considerably confident in your mechanical abilities, get some competent help.
Good luck
Roger
 

zoommx

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#7
oh, my bad. To the best of my FADING memory my kdx had to be split, but it isn't the same bike of course.
 
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#8
Do you think the crank seal would keep it from starting?

I've seen car cylandar heads that have had coolant leaks and they were spotless, no carbon build up of any kind, the mechanic said it was because the coolant cleaned the cylandar. I don't know if I believe that explanation but of the other seven cylandars it was a very noticable differance. But i guess if I have straight oil in my cylander that might over come any "cleaning" effect the coolant might provide.

The oil level was lower so I will be replacing the crank seal. Is this extremely difficult to replace. Does anyone have any past experiece on how best to go about it. But back to my original concern, I would hate to take apart everything and find out that the reason it wouldn't start was because of something else. It seems to me that even with a bad crank seal and a slightly bad head gasket it would still start but run like crap. I have a suspicion that the head gasket may have always been bad but didn't manifest itself until there was enough gunk to to finally squeze out of the head.
As always any ideas are greatly appreciated.
P.S. how long does it take to get an email address here. I applied for one several days ago and I still don't have one.
 
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#9
Sounds like whats happening with my bike. I bought it, and the motor had just been rebuilt. I havent had any crap ooze out of the cylinder, but as far as the running, and starting issues go, it sounds a lot like mine.
 

darringer

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#10
Adstott. A friend of mine has a '90 RM that had a blown right-side crank seal. The bike would run, but was EXTREMELY hard to start, and ran poorly. Was the bike smoking badly before it quit? Usually a bad seal will cause a major smoke screen. If you don't have a manual for the bike, get one. It's worth it's weight in gold. The crank seal is very easy to fix, and not expensive either.
 
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#11
I'm not sure if it was smoking badly before it stopped running. The problem litteraly manifested itself in a matter of less then a minute. I tried to do a hill climb but didn't have enough momentum to make it up the hill, so I rolled back down the hill, and on the way down it died. When I got to the bottom it took several kicks to start (which was unusual, but it did kick start) then I rode it maybe 200 feet and stopped to take a break and talk to some guys before I went to the track. I don't remember it running bad between the hill climb and the track, but I was just "puttering" around. (the rest of the story is in the first post)

Would it be easier to take the engine out of the bike to replace the crank seal? It's starting to get pretty cold here so that is also a factor. (northern IL) I do have a clymer manual, is there another book that would be so much better that it would be worth spending the money on?
 

Bodge

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#12
I wouldnt reccomend removing the engine. That would just make the job 2x as hard lol. About the clymer manual, its probly pretty good. Id check how it is for this job specificly(sp?). My friend had one for his 88cr125 and in the section for replaing the seal it was worthless. The only problems we had when doing the 88's were the powervalve which came apart w/o us looking at it before hand and also the kick start spring.
 
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#13
Replacing the right side crank seal is not too difficult on that bike. You can lean it over on it's left side to do it (tank off and carb drained, of course). The trick is holding the primary gear so you can remove and reinstall the primary gear bolt. I cut a piece of an old gear, about six teeth worth, and use it between the primary gear and the clutch basket gear. I've seen people jam a screwdriver between the two gears as well (shudder!!!) Don't know if I'd recommend that. Once the gear is off, pull out the collar that is behind the gear and you can then carefully remove the old seal. Be careful to not scratch the sealing surface of the crankshaft. Put some grease on the seal, inside and out, and take your time putting it in straight. You should find something that is about the same size as the outside of the seal such as a piece of PVC to drive it in. Again, take your time and keep it straight. After that, button it all back up and be sure to use some locktite on the bolt. I had the nut on a CR80 back off once and try to push itself through the case.
 

darringer

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#14
Another easy way to hold the primary gear is by wedging a penny between the primary gear and the clutch gear. This will deform the penny severely but not do any harm to the much stronger gears. I've done this numerous times without ever having a problem. it works well when tightening the primary bolt also.