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Old 03-18-2013, 10:55 AM   #756
Seavoyage
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Joined: Dec 2011
Location: San Francisco
Oddometer: 133
Big Bore Trials

The Find!: GasGas 1995 JT35 posted on CL and quickly purchased it:


Due Diligence:
The previous owner purchased it in San Jose in 2011 and did not do any maintenance, or ride it much. He bought it from someone who could not start the high-compression motor.

Developed by 7-time World Champion Jordi Tarres (hence the JT model) for GasGas to compete in the World Trials Championship (WTC), this model won the WTC 3 consecutive years from 1993-1995.

This is not a beginners bike! Quite scary!

I contacted Jon Stoodley http://www.gasgas.com/tech.htm , one of the key figures in preserving Trials scene here in the USA. Jon told me that the bike was originally owned by Steve Darrow, a National ranked US Observed Trials Championship competitor. Jon had made some head modification on this bike to make it easier to start. This bike is a 'big-bore 2-stroke beast: capable of 6th gear wheelies. The 327cc engine was the most powerful trial motorcycle produced by any manufacturer until the 1996-1997 338cc JTR370..

The engine design is considered to be bullet proof. Used in GasGas trials models till 2003, it is also used in the 1995 to the current generation of GasGas EnduroCross bikes which have roots in the Cagiva/Husqvarna WR chassis design. The EnduroCross 250/300 uses different transmission ratios, cylinder, and incorporates a exhaust powervalve. Trials manufacturers no longer build these big bore bikes (current models are under 300 cc).

After a few hours inspection, and routine maintenance, everything works!

Due to the heavy clutch use on a trials bike, we run Dexron III ATF fluid in this transmission (or 5W30 Dino oil) and never sythetic oil. The transmission 1st-4th gear are suited for trials, with 5th & 6th set up for trail riding.

The Paioli fork design which was used by GasGas until 2001 (Current GasGas Pro uses Marzocchi), Sherco to 2009, and Beta to 2010. The Paioli RSD fork has only one spring held in the Left fork with 280cc of 5W fork oil. The dampening cartridge is held in the opposite (Right) fork with 330cc of 7.5W fork oil. Bleeding the AJP clutch (mineral oil) and the rear brake (DOT 4) is interesting as you push the fluid up though the nipple towards the master cylinder: as opposed to filling the upper cylinder and letting the fluid drain down. The bike has all the components of the GasGas Factory WTC bikes: Dellorto PHBH26CS replaced with Keihin PWK28 (yes a 28mm!); Kokusan ignition; Boyesen reed valves. You'll notice that a trials 2-stroke does not have an expansion chamber (note the exhaust pipe).

These models are wired for lighting, and were street legal in Europe. I will probably get a CA license plate for this one in the near future.

Nut and Bolt check complete, lubed, and fresh fluids. Replaced fork oil. Tyre pressure set: 7 psi Front/3.5 psi Rear. Fresh 80:1 Pre-mix.Taking her out today to bash some rocks and logs!

Here's the Jordi Tarres video:

First Ride Report: The JT35 definitely feels heavier at around 170 lbs. In comparison the trials bikes over the past decade are sub 150 lbs. The geometry is fine and comparable to more modern bikes, but some bikes have even tighter steering lock. I need to get fresh Michelin X11 and adjust the clutch engagement: I kept on pushing my front in limited traction turns - and I should really lean the bike more and turn the bars less (oxymoron when you are practising full lock turns.)

It feels very planted, and compared to my daughter's GasGas TXT Pro 200, it much more suited for trail riding. Gobs of torque which let's you power through anything, even more so than my GasGas EC300. But relatively a challenge to kickstart with the high compression and low exhaust port. With the proper technique I can kickstart in the first or second kick. Good fuel mileage - we rode 4-hrs. yesterday without refueling.

I highly recommend trials as the foundation for all riders. It will make you a much more controlled and proficient rider.
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Seavoyage screwed with this post 05-13-2013 at 11:11 PM
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