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? Engine Noise And Clutch Adjustment


irishjohn
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What is considered normal engine noise on a TXT 280? After getting this one started (read my previous post), I putted around a bit in the back yard. The engine seems to make more noise than the whirring/exhaust sound I expected. Maybe it needs a ring job. A friend of mine suggested it could be caused by the carb not being properly adjusted.

Second, can someone walk me through the adjusting process for the clutch. Mine engages strong but seems to not totally disengage.

Lastly may I say, using the GasGas as an indicator, I am a bit shocked how much trials bikes have changed since I last road 30 years ago. On my short put around the yard, I felt like someone from the Bronze Age trying to drive a car. This is going to be fun, I have to start from scratch and learn how to ride all over again!

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What is considered normal engine noise on a TXT 280? After getting this one started (read my previous post), I putted around a bit in the back yard. The engine seems to make more noise than the whirring/exhaust sound I expected. Maybe it needs a ring job. A friend of mine suggested it could be caused by the carb not being properly adjusted.

Second, can someone walk me through the adjusting process for the clutch. Mine engages strong but seems to not totally disengage.

Lastly may I say, using the GasGas as an indicator, I am a bit shocked how much trials bikes have changed since I last road 30 years ago. On my short put around the yard, I felt like someone from the Bronze Age trying to drive a car. This is going to be fun, I have to start from scratch and learn how to ride all over again!

As I remember, you have an 03' Pro, so lets look at some outside adjustments before getting into the clutch proper (you will be shocked at this clutch if it's been 30 years). It has one spring, a coned washer called a Belville spring, and a 3-fiber/2-steel disk pack.

The main problem I see with new riders used to cable control, rather hydraulic systems, is that they mistake how the adjustment screw on the lever works and assume that tightening it up will give more clutch throw, but the opposite is true. It's only to set the clearance at the plunger rod that goes through the rubber boot on the master cylinder. GasGas clutches do not totally release as a rule so a very slight amount of drag is normal and it keeps the slack out of the drivetrain. The piston in the M/C must retract fully back to the circlip under the rubber boot so that the bleed hole between the M/C bore and the reservoir is opened so the system can equalize. There should be a few thousandth clearance where the lever adjustment screw meets the M/C piston plunger.

In the 03', you probably will use about 400cc's of a light fluid like Dexron ATF in the transmission and change it about every 5-10 hours max. The crank main bearings are lubed by the transmission fluid, not premix. Try the lever adjustment for a start and see if it makes any difference. Make sure you have the lever adjusted out far enough to get a full throw of the piston, these M/C bores are only 9.5mm and don't displace a lot of fluid.

When I moved from a JTR370 to a Pro, a lot of the lines in my face went away as I quit wincing every time I had to ride rough sections. The reduction of weight was a little disconcerning at first, but you'll learn to let the bike glide over stuff you had to plow into in the past.

Jon

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Jon, you are my GasGas Obi Won!

Thanks for the tips. The differences between my Bultacos, KT250s, Tys, Montesas and Ossas really is unbelieveable. I was putting around in the yard today and loaded the forks to loft the wheel, very little throttle and I was on my back! Even my 350 Sherpa T did not have this much torque. I have to learn to ride all over again.

Any comments on the engine noise? Will the gas octane induce knock? I haven't found a source for 100 octane fuel as yet. With the hurricane fuel shortage scare, 87octane was all I could find.

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Yes - The pro's need higher octane than 87 - min 95. Even then, in hot conditions under load you can get detonation so mixing in some race gas is common. Since it's been awhile since you had a modern bike, I'll also ask what fuel/oil ratio are your running? 80:1 to 100:1 with 100% synthetic is the norm nowadays.

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Jon, you are my GasGas Obi Won!

Thanks for the tips. The differences between my Bultacos, KT250s, Tys, Montesas and Ossas really is unbelieveable. I was putting around in the yard today and loaded the forks to loft the wheel, very little throttle and I was on my back! Even my 350 Sherpa T did not have this much torque. I have to learn to ride all over again.

Any comments on the engine noise? Will the gas octane induce knock? I haven't found a source for 100 octane fuel as yet. With the hurricane fuel shortage scare, 87octane was all I could find.

The Pro's can usually handle 91/92 octane (provided the jetting is correct), unlike the older engines that usually were happy with 95 octane.

A lot of riders use a 50/50 mix of pump and race fuel and I run straight 110 race fuel to soften the engine response as I'm an old geezer who can't ride worth a squat.....;)

Your jetting should be in the range (sea level approx):

MAIN: 107

PILOT: S36 (I think the VHST takes a different pilot from the "normal" Dellorto PHBL used on the other years)

NEEDLE: D48 (2ND FROM BOTTOM OF FIVE)

FUEL SCREW: 3.5 TURNS OUT (to start with. After warm-up, quickly blip the throttle and adjust screw in/out to get best response)

FLOAT HEIGHT: FLOAT ARMS PARALELL WITH FLOAT BOWL BASE

I understand your experience, I came into the more modern bikes of the 80's and 90's from the OSSA and Sherpa T bikes and worked up to the Pro, but you're jumping right in.....:)

Jon

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Forget what Jon says, I would ONLY take advice from this guy....

http://www.gasgas.com/Pages/Technical/gas.html

Seriously, Its nice to have GG experts on the TC site. BTW - they are one and the same if you didnt know IJ.

I wouldn't either, that guy's full of crap.......both of them.......;)

Jon

ps. forgot to mention, you might try lowering the needle clip (raising the needle) one groove to see if it makes a difference, it will give you an indication if the noise is fuel delivery related.

Edited by JSE
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