Broken belt and broken roller - 5/20 problem resolved !  By  dev150cc (Read 6,951 times)

In know, lol.  And taking a video at half throttle on the road is out of the question without a good camera phone holder gizmo.  It's ok, I'll get there.

I completely disassembled the clutch to inspect and clean.  It's in great shape and I found no particles, miraculously.  Springs all pass muster as well.

When I get home, first thing I'm going to do is swap back to the original variator with 13 gram weights and test that.  If the occurrence still happens, check spark parts.  If it still happens start with fuel starvation.  I'm running out of stuff to check...

That was my first thought as well, but his description of what its doing is not explained clearly and he said it was running fine before the belt broke so what is one supposed to think. And as you know different symptoms point to different parts
of a scooter system. I agree though if he has a hesitation around mid- throttle he has a fuel problem there and maybe all he needs to do is raise the needle one notch. But then it could also be that the MAIN JET is to big and is getting to much fuel in the mid range so dropping the needle would fix it or a smaller Main jet.
Alleyoop

When I say strange one I mean the problem not he person , lol

I know , it's probably just not a good explanation . That's what's makin it difficult to pinpoint

how long did it sit with a broken belt ?

John

Ok folks, figured it out this evening when I got home. In short, it was a coil or plug boot progressively going bad over the course of several miles on 2 test runs.

Since this thread bounced around a little, let me roll the tape back and provide the highlights....

Scenario: bone stock bike in great running condition. Variator had 17 gram weights. Topped out at about 50 indicated on the speedo. Belt broke (*I think I know why, see below)
I took the opportunity to install a Koso variator and 12 gram weights while replacing the belt.

Trial ride 1: good ride. Lost some bottom end with the new variator and weights. Gained a few MPH on top end. At about 10 miles in, the engine started skipping out when I tried to accelerate past, say, 30mph if I was too aggressive with the throttle. Felt distinctly like an overheat. Limped it home at low speed, afraid I had burnt up the head. Figured it was just running lean, as is the reputation for the factory setup for these scoots, typically. Unclear if/why related to a variator and weight change. Pulled the main jet - 102.

Trial ride 2: installed a 115 jet (from 102 stock), checked vacuum and fuel hoses, etc. Test right started out right out of my driveway with the same engine skip when accelerating from 20-30'ish with anything but a feather touch to the throttle.

Tonight I got home from work and targeted the variator to exclude it as an issue. Put the old variator and some 13 gram weights in. Fired up the scoot and heard the old variator rattling a fair amount. Not good, pulled it out and put the Koso back in with the 13 grams. Fired it up, ran smooth. CVT glided up and down while on the center stand. Took it down the block and the engine skipped again upon mid-range accelleration if I was too aggressive with the throttle. I was happy this eliminated the variator as an issue.

Moved on to the spark path. I replaced the spark plug and the coil/boot combo with spares I ordered. Test ride: success. Smooth up and down the throttle range, both quick and slow. So in the end it seems either the boot was falling apart inside, or the coil was progressively dying, and it just happened to coincide with the variator work.

* Other things: that old variator, when I put it back in to compare with tonight, made some rattling sounds. I took it out and noticed how loosely the ramp plate fit. It was downright sloppy and you could hear the weights getting jarred inside. Makes me wonder if the original weights were rattled to bits, and the variator performed roughly, killing the previous Gates belt. I'd put my money on it at this point.

The Koso: After my successful ride tonight after the coil unit change, I rode with the 13 gram weights for about 20 miles. It was ok. But I felt it was lethargic. I came home and swapped the 12's back in. Notable improvement in getting off the line - not exactly a rabbit start, but good enough for me to hang with expressway traffic. There is a boring wind-up in speed from 25 to 50 indicated mph, but once I got to 50, it advanced a bit more responsively for another few miles per hour. So I'm very happy a this point. If I could have just a bit more punch off the line up to, say, 30mph, or fill that 30-50mph slow rise, I think I'd have the perfect setup. But very happy so far. I rode about 50 miles tonight after getting the coil issue resolved.

Up-jetting to 115 made no difference in spark coloration. The spark plug I swapped out to looks pretty much the same as the original plug I replaced. This picture is under a fairly bluish light, so it looks whiter than it should, but it's definitely not the coffee color Jerry and others note as the ideal for a GY6 plug. I'll make do, as I don't feel good going bigger than 115.


I made a phone video but it's in swf format. You can see it on my flickr account if you cut/paste. At about 6 seconds and 9 seconds in, you can here the drop - that's not me, it's the engine doing that. This was a short jaunt down my block. No good video, just listen...
www.flickr.com/photos/74745751@N00/14247882693/

So, thanks everyone, for ideas. I had a hunch the other day it could come down to spark cutting out, but had to eliminate the one major intentional change (variator) before systematically moving to other possibilies. I'm glad I up-jetted as well. I'm sure it was running lean before and the 115 jet gives me some assurance I'm not overheating the engine due to gas starvation.

Now that this is sorted, I'll get back to riding and trying other things like getting that carb dialed in for optimal performance.