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.

 

Run the bike with the airbox pipe off after cleaning the carb. My guess is it will look like it is spitting fuel/air mix out of the intake, not sucking it in. Same way as the breather looks to be blowing, not blowing and sucking.

If the belt box was that oily, the crankcase seal must have gone, did you fit a new one? I use petrol that I have drained out of bikes that have had water or dirt in the tank, for cleaning down engine parts. Fire risk means no naked flames anywhere in the workshop when doing this, but it works for me.

 

I am still learning how best to communicate with customers. I started my small engine repair business back in October of 2025 and I have a lot of learning to do, I probably need to find myself a mentor.

I dug myself into a hole with this repair. The quad came from a friend of a friend with the request "See if you can get it running for cheap". When clarifying what cheap meant, the customer said "around $200". The quad had been sitting for years. All 4 tires were flat, the rims bent and rusted, one of the tires was off of the bead. It was very dirty and duct tape was used to fix the holes in the seat cushion.

My gut told me it was a bad idea, but I took a look at the thing and had patted myself on the back after I was able to determine what was wrong with it in 1 hour.

1. Carbon buildup on the intake valve was preventing it from fully seating
2. Manifold boot was cracked and leaking air
3. valve lash needed to be redone
4. Blown starter fuse
5. Broken starter pre-relay (I'm not sure what you call the relay before start relay)

I used carbon buildup chemical to get the valve seated, I adjusted the valves, taped up the manifold boot as temporary fix, and sprayed starter fluid while jumping the starter motor and she started up. Thinking I could make a good future customer, I told him I could repair it for $200. I'm an idiot.

Fast forward 3 full days of work and I have put $175 in parts into it, all without running it by the customer. Why? Because I hate the idea of having the customer pay for repair after repair after repair only to end up with a Quad that doesn't work properly. So, I figured I would just get it to the point of driving around before I called and told him about all of the problems I was running into. I kept telling myself, I can't give this thing back to the customer with this or that broken, and I can't properly test my repairs out with this fixed too. Below are all of the things I ended up fixing:

1. Replaced engine and transmission oil.
2. Bought a new dipstick so I could measure the engine oil level (the old one was broken).
3. The fuel petcock was leaking, replaced it.
4. The carb was heavily corroded. (this was the hardest part, I could not find a rebuild kit that fit the carb that was on there and quality new carbs were outside of the budget)
5. Front left wheel's bead was too rusted, had to remove the rust and reseat the tire.
6. cleaned oil around the CVT
7. Put in a new battery
8. Installed a new drive chain
9. Fixed the drive chain tension.
10. Replaced a few missing/rusted screws and bolts

When the quad arrived the crankcase was full of fuel. I should have swapped out both oil seals while I was in there, but I was already way over budget and I had the excuse that the reason oil got in there was because the crankcase was full of gas for years, artificially raising the oil level. I did visually inspect both seals and I didn't see any new (clean) oil coming through, so I buttoned everything up hoping for the best.

Sorry for the long winded reply. This job has been a learning opportunity for me. The quad still has lots of unaddressed issues. Front brakes do not work. Reverse shift safety switch is broken. The tires leak air relatively quickly. The lights don't work. I have not yet tested to see if the battery is actually getting charged.

 

As an employee I don't need to worry about the financial side, though as many "just give it a service" jobs turn into complete rebuilds, when things start getting potentially expensive I let the boss know and he contacts the customer to OK any big spends. We are at the cheap end of the market and things are getting a lot harder. Our parts supplier has started sending a lot of Chinese stuff in "big name" boxes. Honda 300, 350 and old 420 wheel bearings from them are not lasting a year. Big name aftermarket 350 Honda regulators got so bad the sockets didn't fit the plug on the wiring loom and only lasted 6 months once you filed the sockets down to fit. Some of the cheapest eBay Chinese stuff can work surprisingly well, like Honda 350 carbs, but it is total pot luck and price is more of an indicator of the vendor's greed, than quality.

 

I am going to have to learn the hard way which chinese parts or OK and which ones are unacceptable. Because the price difference between the chinese parts and the OEM parts often makes things worth repairing vs scrapping.

One of my customers dropped off a 2000 Big Bear 350 quad that failed the leakdown test and had very low compression (around 20psi). I was able to order a chinese replacement jug for it that I am 99% sure will get it running for $70 on ebay. There are youtube videos of people using these cheap jugs successfully and at that price point, the customer was willing to spend the money for the repair and labor at $50 an hour.