125-200cc WR125: Need guidance with top end job

I'm having another episode with my WR125. (Why are the cute ones so much trouble?) It seemed to start with some bogging and not being able to get the revs up and resulted with not running at all. This morning, I pulled the carb off and found that the overflow for the float bowl was blocked with mud. (I can't imagine how that happened) After cleaning the carb and replacing the tube I found that when I tried to start it that it was immediately flooded. When I would push the choke in and hold the throttle wide open, it might make a few feeble sounds like it was trying to fire, but still wouldn't start. I pulled the spark plug and it was dripping wet. I could hold it against the head and spin the engine and get spark as the gas dripped off. I went through this a few times before I had seen enough and pulled out the Mikuni and put it on only to experience the same result. After speaking with my dealer who wondered if perhaps my flywheel had shifted again and the ignition timing was badly out. I checked and that wasn't the case. At this point, I was just casting about and decided to check the compression. It turned out to be about 100 psi. Another call to good ole Harold had him suggesting that I remove the exhaust and reed valve and examine my piston for scratches. I was told that if any lines were showing that dirt had gotten in and that was where my compression was going. I saw what looked like minute vertical scratches. So I assumed what it must have been dirt in my engine and that was the source of my woes. After removing the head, cylinder and piston I could clean them up and they didn't look too bad to me. I showed them to a friend who is a fine professional motorcycle mechanic and he thought that the ring had some tiny nicks, but that the piston and cylinder were just fine. He explained to me about how two strokes can get severely loaded and sometimes not be able to clear themselves. His advise to me was get a new ring, gaskets and make sure that the crankcase was clear and it should be good. I came home and after wiping the exposed portion of the crankshaft with a paper towel I could rotate the engine 360 degrees and it would come up coated with a thick film of oil. My questions, if you are still with me are: (1)Who else has gone through this? (2)what are the torque values for the head bolts and cylinder base nuts? (3) How much compression should I have? Thanx in advance. Perhaps one day I'll be answering questions rather and asking so many.

I myself have had many (more then 5) husky 125"s and have found them to be pretty much bulletproof!! The big thing I think is clean the filter alot and oil it with a good filter oil and swab some grease around the base of the air filer before reinstalling, and make sure when reinstalling everything lines up and run your hand in there assuring you have lined the filter up and it is sealed off. This thing means alot with your 2 stroke. If you have sucked some foreign material into your cylinder, you could have done damage to either or all of your cylinder, piston or rings. I'm not sure on compression but 100 sounds low, my snowmobiles are around 140-160. Ask your husky dealer. Specs for tightening things shoud be covered in your owners manual. Good luck and don't despear once set up properly and if you take care of the filter my experience has shown husky 125's to be ALOT tougher then the japanese or orange bikes.

The carb issue with mud has me a little baffled, not sure how that would have gotton in there. Trace your steps and if you figure that one out, let me know to. Thanks

I have been really careful with installing my air filter. There was actually a bit of mud in the boot on the reed valve. I am convinced that at the moments that I was able to get my revs up that there was enough vacuum generated to pull some of the mud that was in the vent hoses in to the float bowl (I did find a small amount of mud in the float bowl also) and what was small enough to get through the main jet did so. I suppose that it could have just leaked in between the carburetor and the boot, but It was in straight and the clamp was pretty tight. I don't know how to prevent that from happening unless I use some form of sealant when I install the carburetor. Apparently very tiny stuff can make big problems. Thanx for the encouragement, it's a fun bike when I'm riding it.

I had some issues when cleaning my bike water would get into the carb from where the throttle cable attached but never any mud? It you are blasting it with a pressure washer it could be forcing it in maybe? 5 or six kicks with the throttle wide open my 125's compression was 120psi.

You might want to check your transmission oil for signs of gas. If the needle valve in the carb got dirt in it, you may have flooded the case with gas, especially since the overflow was plugged. You can take a long zip tie and stick it in the oil fill hole to pull some of the transmission oil out and smell it for gas.

While you are at it with the carb vent lines: The vent lines with a T in them ( I think there are two of them) I normally run up and into the air box. The ones that hang down by the linkage I take a razor blade to split them open on the ends. This way if you are in a muddy ride they are less likely to get clogged up.

Compression is kind of an indicator only. How hard you kick should be the same every time. With the throttle wide open, kick the bike with a consistant stroke until you see no more gains. The number of kicks is kind of irrelevant as long as you kick enough to make it plateau. Johnny gorrilla can probably get 10psi more than you but who cares, all you are trying to do is create a base line for comparison when deciding top end maitenance in the future. With solid consistant kicks you should see in the neighborhood of 175 psi in stock new condition. I feel a drop of 40-50 psi indicates time to do some top end maintenance. At the very least, wipe the cylinder down with some carb cleaner, give it a very gentle hone if you have one and install a new ring. Once again gauges and equipment vary so try to use the same tools every time.

If your 125 is running correctly you should have about a 1/4" of mostly oil in the bottom of your crankcase. This is normal and will show up as a film of oil on your crank when you turn it over. More than this can be an indicator of being "loaded up". My guess is to clean it all up, install a new ring, make sure your carb is clean and all passages are open, new gaskets, clean the filter and button it up. Head and cylinder torques are 15 ft.lbs. with a varience of +or- 1 lb.

Good luck for what it is worth,
Walt

your carb vet tubes can create a vaccume and that will suck mud up into your carb.
n
7602 or motosportz has a vent tube filter to help keep this from happening. other companies make then too, as i do not have their product on my bike (it came with other brand filters on it). do a search and see what shows up.

i had a 140 reading for my compression and it was a very sick pup, ringed it and brought it back to 175. at 100 psi it probably was barely running, i doubt you were holding the throttle wide open while kicking it, i did that when i checked it the first time.

Hi and thanx for the great responses. I had purchased one of the vent tube filters, but it wasn't installed.(a fine lot of good it does in a box) It will be next time that I ride! I used a Snap-On compression gauge and holding the throttle wide open, gave it at least six to eight sharp stabs on the starter, until I got the highest reading possible. I'm glad to hear that the oil in the bottom is normal. I may just go ahead and drain the gearbox to examine the oil while I'm in to this. My parts don't ship from Hall's until Tuesday.

My bike ran poorly when I got it(used), Checked compression and it was 120.
Hall's said it should have 175. My piston looked good so I replaced the ring and head o-ring and a thinner base gasket and my compression is now 162. Not sure why I can't get 175, but I sometimes wander if this is why some of the 125's run great out of the crate, and some of us have jetting issues. Mine does run well now, but I have to run richer than most of you.
GP

That's interesting. I'm looking forward to seeing what my compression will be when I get it back together. I wish now that I had been checking mine all along. I'll make a practice of checking it in the future.

This is great!! I learned something today. Thanks!

I"ve learned a lot of good stuff on this forum. And met some nice folks too.

My Cr125 comp test is 160 psi since new and is still at 160 one year later after 4o-50 hours of use racing and practice motocross. My sons new yz 125 also has 160 psi new and after 15 hours still at 160 psi. I just use a cheap. Canadain Tire screw in comp guage. Both bikes start great and run fine and based on kickstart feel are about the same as new.

What about my crankcase?

I was discussing my situation with a friend who was quick to point out that whatever got to my cylinder is likely still in my crankcase. We were trying to figure out how to flush it while I have the cylinder off. I would rather not have to split my cases, but I don't want to keep having problems.

Most of it should be worked through. Just to make sure you can turn the bike almost upside down and spray PB Blaster, gas&oil, wd-40, kerosene, or something similar in the cases, and it should get it clean.

Good to know not everyone has 175 pounds compression, and I realize there are differences in gauges and kicking ability. Maybe the important thing is to check it every 3-4 rides.
GP

I have a little ritual that I perform after a ride/race where I wash the bike and go over a list (in my head) of items like gearbox oil, air filter, fork bleeders, chain, etc. I call it "pimping my ride" Compression check just got added to the ritual!

Is the compression test done with the bike cold or hot? I would "think" it would make a difference; yes/no?

John,

Theoretically compression should go up with temperature as the parts expand and gaps are reduced. This is in reality a fairly minor consideration. A worn and ill sealing ring trumps these temperature changes completely. No amount of swelling will seal up a gouge in the cylinder either.

I still feel that compression is just a barometer of top end health when used as a comparison. If you check it cold then always check it cold, even though I doubt you can get more than 5psi difference between the two. I also have seen pressure gauges that vary +or- 5%. Also are you using a full 3/4" threaded gauge with the valve stem in the head of the insert or is it a 1/2" gauge and the valve stem is recessed. That small amount is still increasing the volume of your head by several % in a small 125 head. These are reasons why I feel the number is irrelevant. Just check it when the top end is fresh with a few heat cycles and use that number as your target pressure. Always use the same gauge and attachments.

JMO,
Walt

Thanks Walt and that makes perfect sence to me. I didn't check mine when it was new but I will check it in the morning just to see where it is at this point. Ok David it's tuesday got that thing back together and running?