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Post by madnesshero on Jan 21, 2021 21:46:29 GMT -5
Hi everyone. Ive been experiencing issues with my 139qmb(460mm long case). After adding a bigbore kit and changing a broken cvt cover ive lost my ability to start via push button. Now i know what ur thinking, "madnesshero, ur compression is too high bro". Well this might be a minor symptom of my issue but im starting the believe my cvt cover is to blame for the bendix hangup on the compression stroke and here is my reasoning; with the cvt cover off and my foot lightly holding the bendix in place so not to go flying out or jam my starter gear, the engine cranks like nobodies business. With the cover bolted on the starter wont make it more than 1 rotation. Does anyone have any experience with an issue like this?
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Post by aeroxbud on Jan 22, 2021 16:16:14 GMT -5
I found something similar when my wife brought her Aprilia. It was a missing CVT cover gasket.
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Post by madnesshero on Jan 22, 2021 19:44:06 GMT -5
Thats interesting that the gasket thickness makes up enough space to cause a snag without it, ill replace my gasket for sure, good on ya! Also after investigating it more im thinking I found the main issue, i believe that the bendix bushing on the motor (not the cvt cover bushing) is worn out and has too much slack allowing it to kick just enough sideways to jam. So that will have to be swapped also.
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Post by GrumpyUnk on Jan 25, 2021 12:07:01 GMT -5
Whenever I put one back together, I make sure to put a dab of grease into the bushings or on the ends of the Bendix. The fit is not real close, so is it possible that the cover was not getting aligned and the Bendix was being caught outside the bushing area and jamming? I guess I'm chicken because I never even thought about trying the starter with the cover off. FWIW, all the 72cc updates I have installed have had zero problems with the starter being unable to crank them over. They all worked fine, with zero apparent problems.
Do check that the gear rides on the grooves without binding. You should be able to rotate the gear that engages the crankshaft gear, and have it turn and move 'outward' at the same time, and then retract readily with no hangup in either direction. They can get dirty and need cleaning and slight lubrication. If it moves freely in both directions, and engages the crank gear, it should work. I doubt the thickness of the gasket causes the binding, but you could readily test using some 'tabs' of cardboard placed between the CVT cover and the engine, top & bottom, in a few spots, and then tighten the CVT cover bolts snugly. If that clearance increase does the job, you have your answer. The cardboard (Cheerios box, Saltines, or your fave) should equate to a THICK CVT cover gasket. Most are thinner as I have seen.
tom
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Post by FrankenMech on Jan 26, 2021 2:34:13 GMT -5
Are there any sort of locating dowels on the case or cover?
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Post by madnesshero on Feb 1, 2021 13:19:31 GMT -5
Are there any sort of locating dowels on the case or cover? yeah ive got all the case dowels in place, been having a hard time sourcing a gasket for this engine. Starting to wonder if i can swap the left crank case with the 430mm n turn it into a regular long case(because regular long case parts are so much more common than the xl case). But to be as descriptive as possible with the issue it feels like the bushing on the engine (not the cvt bushing) is worn n has too much slack, because when the bendix engages the starter gear the bendix flexes tward the back wheel n jams, this happens with or without the cvt case. |
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Post by GrumpyUnk on Feb 2, 2021 10:13:08 GMT -5
Could be the bushing is worn out... or has become missing. Take a good light and see if it is there, gone, or has an oval shape due to wear. Bushings are cheap, and likely the same size no matter which size CVT case you have as they all use the same Bendix drive. Take a look also at the bushing in the CVT cover. They can also wear, and if someone has replaced the case cover, they may have skipped installing the bushing. If either or both are missing or worn, the Bendix will flop around and engage any which way, and possibly jam as yours does.
The bushings are not a 'tight' fit from what I have seen, but do keep the Bendix somewhat aligned, enough for it to work in most cases. Most times the Bendix shafts are hard enough that they are not the wear point, it is the bushings which are made of softer material, and wear, especially given they are somewhat hidden and don't get much attention even though they are used almose every time the bike is used.
tom
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Post by madnesshero on Mar 18, 2021 13:35:29 GMT -5
Just wanted to come back here for completion of the post to help others.
Me n grumpyUnk had theorized the crankcase bendix bushing was worn out, and this was exactly the issue. Replaced it in 20 mins and now im cranking no problem.
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Post by captincvmn on Mar 18, 2021 17:06:22 GMT -5
Just wanted to come back here for completion of the post to help others. Me n grumpyUnk had theorized the crankcase bendix bushing was worn out, and this was exactly the issue. Replaced it in 20 mins and now im cranking no problem. Don’t be a stranger. Visit often |
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