My Intro

[Aqua]

Hi guys I just installed a 2 stroke china engine to my vintage 1993 proflex, what a pain in the rear! Anyways I am from BC Canada, and I am a gal who sadly knows little about engines but hey gotta learn somewhere.

 

[Happy Valley]

Hello and welcome to MBc.

Hmmmm, '93 Proflex. What model is that? Dual suspension with the cross link front fork?

Curious because I've only seen two Proflexes here, mine a '98 Animal and one that AlaskaVan has.

 

[give me vtec]

welcome to the site... please ask any questions you might have.

 

[Aqua]

Hello and welcome to MBc.

Hmmmm, '93 Proflex. What model is that? Dual suspension with the cross link front fork?

Curious because I've only seen two Proflexes here, mine a '98 Animal and one that AlaskaVan has.

This is one of the first ones, its the 753 model it only has the rock shox indy FS, but I found a source for elastomers for it and replaced the rear good as new.

(not mine but exact same model)

http://foto.mtb-forum.it/data/500/medium/pro-flex_753.jpg

The question I have is my main issue, figuring out the chainline... because every time I sit on the bike the chain loosens just enough to jam.. driving me nutz!

 

[Happy Valley]

Yeah, there's an intro period before posting links is possible....but with your permission:

http://foto.mtb-forum.it/data/500/medium/pro-flex_753.jpg

So is the chain issue you have is with the original bike drivetrain or the engine chain?

BTW, this is mine, before and after:

 

[GearNut]

You will have to fabricate a spring loaded chain tensioner to push against the lower chain run. This will take up the varying chain slack created as the rear suspension cycles up and down.

 

[Lazieboy]

Yo what up.

Hi. and welcome. This is where all your answers are. Pay em forward.

 

[Aqua]

You will have to fabricate a spring loaded chain tensioner to push against the lower chain run. This will take up the varying chain slack created as the rear suspension cycles up and down.

Yes, this is what I figured. Any links to examples of anyone doing this?

@Happy Valley I have no idea why I said indy but I meant quadra shock on it, a little early for the indy models, lol

Heres some pics (sorry for quality I was too tired to seek out my camera charger )

http://imgur.com/hL7RA.jpg

http://imgur.com/1JadN.jpg

http://imgur.com/xOtk2.jpg

http://imgur.com/w6pGM.jpg

It looks like it should work, right? but no, unfortunately because of the little but of slack in the chain, it jams and then puts so much force on my little chain tensioner creation it usually bends it into the spokes.



The other issue is due to the small spacing of the rear suspension chainstays the pully has to be very low and close to the rear sprocket to give tension and not hit the upper chain.

 

[Neon]

Aqua. I thought you did an excellent job of jamming the engine in the bike. Putting on the spring tensioned roller should solve the chain slack problems. Could try mounting the roller on the rear swingarm supports just above the top of the chain.

 

[Happy Valley]

Nice job of mounting!

FS bikes can be problematic finding the right chain tensioner arrangement with the HT frame mounted engines. The configuration of that model PF swingarm exacerbates it somewhat though the good thing is the limited travel with the elastomer rear strut.

Hopefully you can find a spring loaded arrangement that works.

Here's just a sampling of DIY solutions:
http://www.motoredbikes.com/attachment.php?attachmentid=19348&d=1246545040
http://www.motoredbikes.com/attachment.php?attachmentid=19782&d=1248404705
http://motorbicycling.com/attachmen...ner-motorized-bicycle-moped-part-dscf1689.jpg
http://motorbicycling.com/attachmen...pring-return-chain-tensioner-may-2008-008.jpg
http://custommotoredbicycles.com/sp...zed_bicycle_home_made_from_original_tensioner

Thing is will there be room? Ya know, this is an ongoing issue for many so the archives here might yield an idea also with a search query like 'spring loaded chain tensioner'

Another whole ball game would be a shift kit however can't say how it would work on your bike.

Lots of creative folks here so there's bound to be a way to make it all work.