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rizzer 06-23-2011 10:10 AM

Trials Bike Build/conversion?
alright, I've been losing sleep over this...I was wondering if anyone have done or seen a trial bike built from non-trial bikes? say a dirtbike converted to trials or the likes.

been browsing around for this but couldn't find any on this forum, and it seems like Google can't help me either.

see Trials are expensive bikes in my home country (Indonesia) and I don't think I could ever afford one back home. So I'm thinking of building one from a dirt/street bike, but need a lot of reference to compile. Has anyone here gone through the trouble of building one? or seen a thread of a build?

any info would be much appreciated! :)

rizzer 06-24-2011 04:15 AM

no takers???? alrite, I'll go back to my corner :(:

BikePilot 06-24-2011 04:52 AM

I think to make a modern trials bike from a dirt bike would be very expensive and extremely difficult to get anything remotely competitive. Maybe look into shipping a used trials bike home from the UK - they are surprisingly affordable in the UK. Have a close look at pictures of a modern trials bike - everything is extremely compact and it'd be rather difficult to get anywhere near that compact using dirt bike parts. Just getting the exhaust right would require some serious fabrication skill, then there's the frame, major engine work (you'd probably need to essentially make your own cylinder to get mild enough ports and a small enough intake port to work with an itty bitty trials bike carb), suspension (you won't get enough steering lock with modern dirt bike forks - too fat), wheels (rear needs to be tubliss - not too hard to do, but not free)...

Back in the old days folks did convert bikes to dirt and trials, but that was before bikes got very specialized and they really weren't very good :lol3

You could probably make something that wouldn't be too far off from say a Beta Alp or Gasgas Pampara by really stripping down a bike like the KDX 200 and fitting trials tires.

lamotovita 06-24-2011 07:03 AM

A Trials motorcycle is just that, a motorcycle, ride what you've got.
Here in the U.S. at least, Novice sections can easily be mastered on a decent trail bike. Things to consider modifying on a bike include, grind or cut the steering stops for maximum turning (air cooled bikes frequently have more room than liquid cooled bikes), make sure very low gearing is available for the model you select as well as clearance for a proper Trials tire. Remounting footpegs can be very helpfull as well.
I don't know what bikes you have available so I can't make any specific reccomendations.
Riding Trials is about mastering what you have, not having the same bike as the world champ.

BikePilot 06-24-2011 07:47 AM

I definitely couldn't ride a novice section in D6 on a non-trials bike. Sure I could do the big obstacles then blow the section boundries, but the sections are way, way too tight for a big bike. I'm newish to trials so maybe not the best proof its impossible (and its probably not), but it'd take someone very good at hopping to pull it off at the least. I cleaned the day in my class on a trials bike and have run top 5 overall in Vegas to Reno so I'm not a noob to bikes generally. You certainly don't need a trials bike for obstacles - in fact I'm not even sure a trials bike is all that great for most big obstacles, but a trials section is super tight, and to maneuver in such tight confines a proper trials bike is pretty necessary.

I could probably ride the 4 line in a vintage event on a non-trials bike (or my pickup truck :lol3) though. :deal

I completely agree with ride what ya got, but he asked about a trials bike.

rizzer 06-24-2011 08:16 AM

yeay!!! repliesss!!!! :D

Bikepilot, do you have a list of specifications like frame dimensions, rake, wheel sizes etc to refer to?
I do agree that it's gonna be A LOT of work, but still a better chance over importing as we have a no used CBU import policy. and for those new CBU imports, they're subject to 180% tax of the invoice price :cry

btw,that gas gas pampera looks pretty cool actually :)

Lamotovita, I like the spirit! :D another problem would be the base bikes/engine for the project actually. the biggest 2 stroke available on the market is a 150cc kwak ninja. we also have a range of 200-250cc 4 strokes but I don't think the weight of them would be ideal for trials. then again, I see back in the day they also used to have heavy brit bikes for trials.

I'm guessing trials have their power bands in the lower rpms, so longer strokes over bore? or would it be enough just to lower the gearing of a mid range powered bike?

I've also noticed on 2 stroke trial bikes, the expansion chamber starts a bit further back than it would on other purpose built 2 strokers. does this affect the engine character as well?

sorry for all the questions guys :D

gloud 06-24-2011 08:28 AM

Can you mail/ship parts to yourself ? If you could get a frame and suspension from ANY trials bike you would be ahead. then you could re-engine it at home.
I have done conversions engine wise, and while you could play at trials without heavy flywheels it was hard to keep it running.

rizzer 06-24-2011 08:41 AM

Gloud, yes. I've actually shipped some suspensions back home for my original project which was supposed to be a street fighter/supermoto themed build. But I've just recently caught this trials fever and I don't think I'll be able to use those parts for trials...looks like more shopping ahead. Still got taxes paid on them (25%) but at least they got home safe. Sadly, since the beginning of this year, there's no chance to send a frame (unless illegally). dunno what the sense was in that regulation actually

what's the length of a trials fork btw? how much travel?

ah yeah, thanks for pointing that out (heavy flywheels)...I used to lighten them for drag racing back in the days. now I'm heading the opposite direction :D

gloud 06-24-2011 09:43 AM

I don"t have a modern trials to measure. i would lean towards a twin shock /vintage bike for ease of construction. You will need a steep steering head angle, So it will turn quick, and soft suspension then clean as much stuff off it as possible, and get a tiny tank for it. add competition trials tires and it would be a start.

lamotovita 06-24-2011 10:02 AM


Originally Posted by BikePilot (Post 16242944)
I definitely couldn't ride a novice section in D6 on a non-trials bike.I completely agree with ride what ya got, but he asked about a trials bike.

I don't know where D6 is but I'm guessing you mean that you couldn't clean novice sections on a non Trials bike. If you're cleaning every thing you ride it's time to move up a class.

I guess what I'm trying to say is that a Trials bike is the bike you have to ride Trials on.

rizzer 06-24-2011 11:19 AM

been browsing around for some references and found a group of local offroaders with trials (looking) bikes.

the vid is pretty funny too :D
and looking at the upload date, looks like I've missed A LOT

btw, how do u embed a video? :/

rizzer 06-24-2011 11:25 AM
and found a home-made trial pic :D
looks like an engine from a yamaha RX-135 or RXZ-135
and the white yammie behind it looks cool as well

deminimis 06-24-2011 12:06 PM

Any bike will do IF you wear a funny helmet!

Actually, if I was in your shoes, I'd grab a good older reliable and light (for its era) bike (not necessarily a "dirt bike"), then I'd start removing parts and whittle the bike down to its bare minimum. They did some pretty amazing stuff on old Triumphs way back in the day, for example.

deminimis 06-24-2011 12:12 PM

In fact, here's a '63 Triumph Trials Cub. I'd head in this direction. Just looking at this piece of art makes me go all rubbery.

pookiebear 06-24-2011 01:01 PM

weird. It feels like you been reading my mind.
Here was my thought.
Take a TW200 (the old front drum brake model just because I like simple and it has kick start)
Get a gas tank like the one in the post above. But plastic for lightness.
Change the rims/spokes out to get them into trials sizes.
Get some trials tires.
And a bigger rear sprocket to get the gearring lowered.
Take off all the electrics and mirrors. Take off the passenger pegs.
Cut the seat down.
Get some nice handlebars and wider pegs.

Would be a nice dependable bike. AND it would be an awesome trail bike and a semi good trials bike.

In fact my next trail only bike will be this. I am going with 18 inch rims front and back using the stock front rim size. Going to use knobby REAR MX tires on the front and back. Going to get one of the universal gas tanks from justgastanks dot com

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