91 cr125 running bad, making the boo-wahh sound

[Lonewolf]

i have had problems with this bike since i owned it. i does not do this all the time but most of the time it does. well you really get on the gas from idle it makes the boo-wahh noise and tries to stall. i have been doing my best to try to figure out the problem, i took it to a local shop and the bike sat there for a month only to have them tell me it was a bad ground for the cdi but that didnt fix it. ihave been trying to do my own reaserch on this problem using the internet and im stumped. my bike seems to blow a lot of oil out the exhaust, i has a newer top end, i mix the gas at 32:1 with klotz oil, it has a fmf fatty pipe on it and i have stock jetting according to what the service manual calls for. i have found some info about this but they said it is from a lean condition, but how do you explain the excessive amount of oil blowing out the exhaust, i also read about a possible crank seal on the clutch side being bad and the oil is being drawn into the engine and being burnt, but the bottom end of the motor was rebuilt at the same time as the top end and the oil in the transmission is never low and is its normal color. i seriously dont know what to do, could it possibly be jetting? also the shop i took the bike checked out the electrical stuff and they said it was ok other that the bad ground. the bike runs bad 8 out of 10 times i ride, it seems to change with the weather too. if anyone is interested in helping me figure this out once and for all, it would be greatly appriciated.

 

[Glitch]

If it were to go booowah the way you described, that sounds like a lean pilot jet, you can try turning the air screw in a little to richen it up alittle and see if that helps. The spooge out the silencer indicates rich though, so maybe your pilot jet or air screw is lean and the needle and main jet are rich. So to figure if your main is good you should do a full throttle chop test, do a search for info on that, but also go to Eric Gorr's site.
First, attempt turning your air screw in a little to see if that helps with throttle response, then you can worry about the spooge and the rest of the jetting. Also, what type of riding do you do, it might help to run an '8' heat range plug instead of a '9' if you do more trail and slow riding, but if you ride mx then stick to the 9. eg. B9ES to B8ES.

 

[Joepro9]

when you change the oil are you noticing less oil from the case when franing it? Sounds like maybe a dirty carb, clogged jet, or just very bad jetting. Have you cleaned the carb lately?

 

[Lonewolf]

thanks for responding, i cleaned the carb out not that long ago so i dont think that is the problem. the oil is red just like it was when i put it in and is at the full level. i am using an ngk b8es plug, i tried to start the bike up today and the plug was saoked in oil. i have the air screw set on 2 turns, i dont remember what jets are in the carb, i cant remember what the numbers were cause i changed them a few months ago, i can tell you they are what the service manual calls for. im gonna play with it tonight maybe ill get somewhere.

 

[Joepro9]

id plug is soaked ur fouling, which means your rich on your piolet and or possibly the needle.

 

[Lonewolf]

i did a search for a full throttle chop test and came up with no matches, in fact every time i search for anything i come up with no matches. if possible could you explain how to do this test. i also checked out eric gorr's site many times, i have found some good info but nothing on the full throttle chop test.

 

[Joepro9]

I have never done a chop test, I always jet to what runs best. Where in pa do you live?

 

[Lonewolf]

i live in jefferson hills, its kind of hard to describe what its near, i live about 10 minutes from century three mall, im about 15 miles south east of pittsburgh. i know where blairsville is, it really not that far from me, my friend used to drive to blairsville five days a week to go to vale tech, i see signs for blairsville on 119 on my way to school, i go to westmorland county community collage eventhough i live in alleghny county. anyway, back to the bike, i just got finished messing with it, it wont even run now. i played with the air screw to try to see what would happen if i richened it up, i actually ran for maybe 5 sec. then stalled, i turned it back to how i had it then took out the plug and cleaned the oil off it then started it up and it did the same thing, i tried starting it again and it wouldnt run, im so sick of this damn bike. i am actually trying to get it to run right so i can sell it and buy something newer. i was gonna try to keep it and do a few things to it performance wise but i dont thinks its worth it anymore, i have had enough. i dont think the bike is running lean, there is oil dripping out where the pipe and silencer fit together at, the plugs alway oil foul. i dont know what to do.

 

[Joepro9]

personally I think its so rich it stalling itself out. I was born in pittsburgh and my parents are both from pittsburgh, I have many relatives there. Is your friend still in school there? they are building the new wyotech(they bough valetech) smack in one of the fields I ride in, lol. Your bike puzzles me, could this be and electrical problem? I had similar problems when my cdi went bad.

 

[Big Daddy]

Try using the choke while driving. If the bog goes away, your to lean. I think Eric Gorr's book said to use a #1468 needle. I had this problem with my 1998 cr 125 and the needle had to be changed from a 1370 to a 1468(#16012-KS6-004) this will richen up the midrange. I still have black goo coming out of the pipe. But the bog is gone. I doubt changing the pilot jet will fix this.
HP-2 oil, FMF fatty, Boyesen Rad Valve, 12-51 gearing, 1468 4th clip is what I have.

Good Luck :yeehaw:

 

[Lonewolf]

i tried it with the choke on and half way on like i read on eric gorr's site and it made it worse. i am going to just take the bike somewhere and have them look at it again if i cant figure this out.

 

[NO HAND]

When I had a 91 cr 125, I ran across symptoms like this to find out the cdi was toasted. It was burned up after I had the frame welded. The current from the welder blew it up.

The other thing I can think of: is seized power-valves in the closed position. The bike runs all right off idle but will be way too rich as the rpm goes up. Check by removing the left side power valve cover and see if the pv slide out properly when the rpm goes up.

 

[dstaton]

I have a '93 CR125 with a similar if not identical problem. So far, I've adjusted the float setting, checked the function of the power port valve, (they move out and in relative to engine RPM. I raised the needle to the 4th slot. This was to help off idle response. My air screw is at 2 turns out. With everything set like this, and jets and needle as standard, I do not get splooge. Still I foul plugs. (BR9ES) Today I checked my choke plunger/idle set screw. I removed it from the carb. On the side of the small slide there is some scoring. I replaced it, and screwed the idle screw all the way closed. I started the bike, and there was a noticable difference in response. It was much better. I the adjusted the idle, and it seems to run fine. I'll try it out tomorrow. It shouldn't be raining.
Also, I drained the exhaust accumulations from the cylinder. Approx. 1 - 2 oz drained out. Is it possible that this could feed back into the cylinder and contribute to the fouling?

Until the plug fouls, the bike runs very well.

 

[Lonewolf]

thank you all for responding, i really appreciate it. the bike shop that i originally took it too said they tested all the electrical stuff like the cdi, coil, etc... they said it was ok. they also cleaned the carb, set the float, and they moved the clip on the needle to the very top groove. you would think that if it were a jetting problem and having the stock jetting it would at least run better than it does now, i realize that stock jetting is rich but i am now thinking there is something else wrong.

 

[cr25096er]

i had a 91 cr125 that would like pop n studder on high rpm's but i never figured it out. the left side crank seal was toasted though and still leaked after i replaced it. though i think the cdi was toasted. try swapping it out w/ another 91cr125.

 

[Lonewolf]

that would be a good idea to swap cdi's but i dont know anyone else that has a 91 cr 125 and if i got t a new one and it turns out that it is not the cdi almost all parts places will not take electrical parts back on return so i would be out $250. i just remembered when i was putting the top end together my one friend told me i should dump some 2 stroke oil down in the crank case since the bottom end of the motor was new too, stpupid me actually listened to him. when we went to start the bike it fouled coutless amouts of plugs. maybe all that oil is still in that crank case, i figured it would have all blown out by now though, i might take my top end apart this weekend to check this out.

 

[Joepro9]

do those bikes have hte little power valve actuator you have to line up? I know my 250 does, and if it was not lined up, the bike would not make use of the powervalve. it it would run like crap. I think someone else though possible powervalve, maybe it is.