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bobber job

What Would You Chose As An Aircooled Engine For Your Ulltimate Twin Shock.

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Best motors I've had to ride would be; the Fantic 200, (light, reasonably narrow, reliable). An Aprillia climber rotax, beautiful power, pull from nothing in any gear, (water cooled so probably not eligble for twin shock class). And my Gas Gas JT35, (super reliable, and heaps of grunt)

My advise is to figure out your riding style and what sort of power delivery best suits

I like motors that pick up immediately when I open the throttle, so massive flywheels and slow acceleration I don't like, preferring to use the clutch and rate of throttle opening to control things. Especially when 2 foot away from a big step, (big for me that is) accelerate NOW dammit!!

And as mentioned above good handling etc allows you more chance of being in control so you can get on the power and make the most of it.

After all grip (for a given surface) is a function of weight distribution, suspension geometry, and power delivery. Not forgetting tyre condition.

Building a bike check out "Trials Australia" website, - Forums, (new posts), - Twinshock, & classic,- Steer clear. Very good info for setting up a bike.

 

Hope this helps

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 At our vintage event this weekend a gentlemen built a complete frame around this engine. Tank in the frame tube, falcon shocks, tl front end and xr wheels and brakes. Wish I had taken a picture now.  http://www.ebay.com/itm/Piranha-140cc-Pit-Bike-Engine-crf50-atc70-crf-50-70-atc-/390887546230 I rode it shortly after helping with a slight repair that got him through the weekend. I was actually impressed by the power of such an affordable build. I think it would have been a fun project and an easy to adapt to bike to ride in a short distance trials.

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 I'll put in a vote for the Ty250 motor, for overall ease of use,maintenance,etc,etc, they are hard to beat. Especially if you want to learn to all your own spannering.In standard form they will cope with just about any situation and a massive amount of abuse, farmers and kids,(Mine included) have tried and failed in most cases to wreck them. The current one I'm riding tomorrow night at a local trial is an old Ebay purchase from a breaker,covered in cow poo when I bought it... The engine was a bit of a mess,but has gone back together as a cheapy, I just used bits out of boxes to nail it together,s/h piston from one engine,barrel from another etc. Its all well worn and rattles well.But apart from the noise its a real treat,pulls like a train,screams like a banshee as well,more poke than any one of these I've ridden before.Perfect spread of gears and easy to tune, you have to remember Mick Andrews knew a thing or two when he went to Japan all those years ago. Ok, its not a modern Gas Gas, but ridden it trials it was designed for there isn't much to beat it.

post-3125-0-82349800-1471376948_thumb.jpg 

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Interesting to read peoples opinions, I suppose what we are looking for from an aircooled engine now is very different from the 70's / 80's & early 90's.

In the day the bikes were ridden by riders in their prime doing full Nationals and OTC road Trials Etc.. We'd think nothing of losing 80 or more marks every week.

 

The sections and events the bikes are being used in now have changed, not many mud bogs and climbs now and severity is far, far easier. Tighter sections on closed courses. People using a Twinshock tend to be over 40's, often riding easy routes in trials such as Kia rounds. Several lads have demonstrated even an 80cc bike is capable enough so hardly surprising the little 156cc Fantic is a popular choice.

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When did riders start using the clutch all the time, look at period photos of Rathmel ,Lampkin, Birkett and all the other aces and it was all about throttle control not ultra tight turns.

As has been said above trials has changed and the requirements of the engines also, now more important to get a light clutch, or stronger fingers !

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For torque and smoothness the Rotax, best air cooled is the one of the Aprilia TXR.

For a good all around performance and lightness the Montesa Cota 242, 304, 307 and 309 engine.

In small capacity classes the Fantic engines as already mentioned model 200, 240 or 300.

The TY for 125 pumped with better carb exhaust and so one or the Rotax the Austrian engine is better.

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I'll give you one that will still be running when all the others are holding up some Chinese flyoer.

 

Yamaha YBR125 as was used in the 4 stroke Scorpas.

 

Vitually unbreakable,cheap as chips,loads on ebay

 

Nice and quiet runs on a teaspoonful of fuel. 

 

Ok they're a bit tall and the gearings not perfect.

 

Had one ten years other than a couple of plugs and oil changes it's untouched and this bike gets well used.

 

Best bike I've owned and most fun.

 

 

 

 

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I did expect some to recomend the TY 250 and the 250 325 Suzuki RL too, Must say i did not expect the yamaha ybr 125 to get a mention though.

 Interesting little engines they are how would you go on with the fuel injection though?

  Could you run it with a Capacitor bank, or would you have to have a batery ?

Is not the Zonchen 200cc chinese engine a YBR125 clone, earlier Zongchens were similat to little SR125s or looked very like them.

Edited by bobber job

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Right enough the later ones are fi but the standard carb is an easy fit.

 

The flywheel from earlier ones can be swapped with the later fi ones .

 

Have to blank of the hole where the starter motor goes.

 

I forgot all about this been a bit of a puddin .

 

Best go for a old pre fi one it'll be fine. 

 

Don't know about the Chinese ones might be fine.

 

Get a shot on a wee Scorpa and see what they're like.

 

 

 

 

 

 

 

 

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