I am working ona 2000 Yamaha Breeze 125. It was in rought shape when I received it and I am working through issues as they pop up. The quad had been sitting for years. I was able to get her running again, but I need your help with the following issue:

I don't trust the transmission yet and I don't want to make problems any worse. So, I haven't pushed things hard at all. Low rpms, less than 5mph in reverse.

Nuetral: Runs as expected
Reverse: She seems to be driving fine at slow speeds. Going into reverse at idle is fine, coming out of reverse back into neutral won't work (the shifter is just stuck). As soon as I turn off the quad, I am able to shift around without any issue.
Forward: It slips. It seems to only transfer power to the wheels on a smooth surface and going slightly downhill. When shifting into forward at idle, there is a clacking sounds during the transition. Shifting back to nuetral works just fine.

Other Notable Symptoms: There was old oil in the vbelt and when I was tuning the carb, it starting blowing out of the CVT cooling vent at the front of the quad. Made quite a mess. There is positive crankcase pressure due to piston blowby, that I have not decided whether or not I am going to fix (customer budget dependant). Since the oil was old, much darker than the new oil that is in the crankcase, I am thinking it seeped past a bad seal while it was sitting for years. The oil that was in it when I first got it had gas in it.

Thoughts: I am thinking maybe there is an issue with the clutch. I worry about the old oil intermingling with the dry centrifugal clutch. I was thinking my next step would be to take the cover off of the clutch and inspect it.

Let me know what you all think. Any advice and ideas is greatly appreciated. This is only the 3rd quad I have worked on and I have a lot to learn.

Lorne

 

All single cylinder engines have high crankcase pressure, as 125cc of air is pumped out when the piston goes down, except those which have a one way valve breather like a Briggs Stratton and any quad I have come across tries to expel a cylinder-worth of air on the downstoke and suck in a cylinder-worth on the upstroke, via the breather. An oily belt is going to slip, as will an oily "dry" centrifugal, though one would expect the same in reverse. I have a feeling Breeze reverse is very low geared though, so it would require more power through the belt to go forwards. If a new oil seal and a spotlessly clean variator doesn't fix it, I would guess at a gearbox problem.

 

Like merryman said get oil dried out and cleaned also if the belt is damaged or broke in places it could cause clutch not to full enage cause transmission not to shift into forward and reverse also section of the belt could be hitting the cause housing causing the clunking noise so I would remove the belt housing and inspect and go from there

 

Thank you for the advice ya'll. I will be pulling the cover off tomorrow to inspect the belt and the clutch. I saw in a video that I need to be careful not to let the starter mechanism/gearing come apart while taking off the cover.

Merryman, I wanted to dig in to gain understanding regarding a comment you made:
I'd like to be able to distinguish between a normal amount of crankcase pressure coming out of the breather tube versus too much. And to be clear (since we were talking about the V-belt breather tube earlier) I am referring to the crankcase breather tube that connects to the air intake that feeds into the airbox. When I pull that tube off while the engine is running at idle, there is a continuous flow of air out, about the same amount of flow as if a human was blowing continuously through the hose. To me, this seems like too much. My understanding is that the crankcase pressure created by the piston moving down is offset by the pressure created by the pistion moving up, so that there shouldn't be a net positive or net negative pressure when the engine is in good running condition and that any significant net positive pressure in the crankcase would be due to piston ring blowby.

Two questions:
1. Am I understanding everything correctly? If not, help me understand better please.
2. Is the amount of positive pressure I am feeling with my hand coming out of the breather tube too much?

Tomorrow I am going to do a leakdown test, that way I don't need to be making assumptions about piston ring blowby.

Thanks to both of ya'll for your time and input!

Lorne

 

"Am I understanding everything correctly?" No, as I wrote above, 125cc of air is displaced downwards by the piston on the downstroke, it has to puff out of the breather. 125cc of air is sucked back in on the upstroke, as it happens so fast, not all the air gets out or back in but there is a fair puff that does, for some reason you don't notice the air going in as much as that going out. It shouldn't be all that oily, as the breather system is long enough so oily stuff does not get to the end of the breather tube before being sucked back down the pipe. Get the transmission working right before worrying about blowby. If the bike burns oil it will probably have worn rings and or cylinder.

 

Update:
I need to purchase a recirculating cleaning station. I blew $15 going through multiple cans of non-chlroniated brake cleaner. After cleaning the CVT area (oil was everywhere, see photos) and reassembling, forward is now working. It seemed like the CVT sometimes need a little more throttle to get the thing rolling if the CVT abruptly stopped at high great ratio. Seemed like the amount of throttle needed to get the thing rolling in forward varied more than I would have expected. I am guessing that is normal for a CVT.

The midrange performance seemed off, so I am going to pull the chinese clone carb off today and make some adjustments (it has the wrong size jets on it and has been a PIA to get right).

Thank you merryman, that is what I needed to make sense of what I was experienceing. To test that, I held my finger over the breather tube figuring if it was mostly outbound air, I would feel pressure build up under my finger and if it were back and forth and I could only feel the outbound air, I wouldn't feel any pressure buildup. Not sure if the test was valid, but none-the-less, there was zero pressure buildup. As I am typing, I am also thinking that if blowby exists, it would probably exist both directions and not neccesarily effect the net crankcase pressure. Anyway, it is good for me to think through these things, I appreciate the help and the back and forth.