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Trials Engine Cylinder, Piston, Tranny, Bearings, Clutch, Pipes & Silencers, etc.


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  #1  
Old 10-15-2016, 03:06 PM
Miner Miner is offline
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Default 2007 GG TXT Pro 250 - Starting Issues

Folks, new to the forum, GG and trials generally.... can be found on other forums under same ID.

Just bought the above as my first trials bike.... the guys who make this look easy must be magicians! Hard, especially in soft sandy stuff!

Bike is ok for its age, used but used ok and looked after well..... seems to have starting issues, or you need to be a 2T Jedi to get the thing to kick!

Sometimes I can start it ok, other times I can't get it to fire at all. Couldn't get it to start whe it was hot (outside also, low 30's, moderate humidity), was running ok but when I killed it to take a break, it wouldn't come back.... had to push it home! Tank says 3.1L, wasn't on reserve but took 1.9L. Kicked over after a few kicks but the bike was a lot colder. Tonight it was difficult but went after a few kicks, run it for a bit then tried starting it again..... would fire!

Founds lots from.... just tricky to all sorts of issues! Bike idles and runs ok, responds ok to choke, revs maybe hand a little on deceleration. Only had it a few days so no chance yet to strip and check, was running ok for its previous owner (guy in our off-road group).

Bike generally ok so assume something fickle about it....

Bike did the same again today......!! Brutal!

Was out yesterday, started after a few kicks, no issues. Stalled it climbing an obstacle, couldn't get it to go..... several attempts, switched to reserve, few kicks and away again. Ok till I got home. Filled it today, only took 1.5L..... wasn't out of fuel.

Out today, a good bit earlier so a good bit warmer, took forever to get the thing kicked over..... several minutes of attempting/ranting at it. Ran ok after that..... stalled it after climbing a small obstacle. Couldn't get it to go again. Tried every trick I could muster..... nothing, no chance of getting going.

Had to walk back in mid 30's heat for about 40 mins with the bike, had to stop in the shade and rest as was close to keeling over..... bike was close to being torched!

Going to strip it down next weekend as I'm on track at Yas anyway..... suggestions for things to investigate most welcome.


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  #2  
Old 10-17-2016, 07:05 AM
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Dirt Dud Dirt Dud is offline
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Try an Iridium plug. Tip the bike over until gas comes out the vent and get it to top dead center . And give it a good kick .
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Old 10-17-2016, 08:32 AM
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My 2002 280 TXT Pro and my 2005 2.9 Sherco both had lean choke jets that required me to tip the bike over to make richer to start when cold. The fix is to replace the choke jet with a richer one or drill it slightly larger.

Your bike sounds like it has a different issue because it sounds like it starts ok when it is cold. Have you checked that it has spark when it dies? Does the spark plug look very dark/rich or wet? Does it smoke much when running?When you are kicking it does it help or hurt if you crack open the throttle while you are kicking it? Does it ever start when warm?

One more bit of info. Th GG Pro trials bikes have a somewhat fragile starting parts. I was told by a GG Trials guru to put your foot on the kick lever, rotate it slightly until the slack is taken up, then kick it through the stroke.
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Old 10-23-2016, 11:47 AM
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Got the bike stripped today.... findings:

Carb boot had come loose on the airbox side, bike had sucked in some dust and was on the plug.

Carb stripped and cleaned, a little crud in the bowl and float bowl plug/jet.... how do you measure the float height? Float needle was a little sticky..... square needle in round jet?!

Reeds ok.

Intake/crank ok. No water only either gummed old premix/carbon or maybe a little gear oil..... hard to tell.

Plug wet/fouled..... had a few goes at starting to get the fuel through. Plug dark but cleaned up ok, some crud from bypassing of the filter. Gap was slightly out of tolerance (0.7-0.8 instead of 0.6-0.7), cleaned the plug up and set to 0.65.

Spark.... wasn't convinced at first, didn't look clever and wasn't convinced. Checked it later however when in the garage, then noticed it was crackling in the magnetic bolt dish but a good strong blue arc from the dish to the cylinder head.... should be ok.

Compression.... ~134psi after several stiff kicks. Looks ok. Anyone got a reference value?

Never stripped the exhaust off.... need to take the shock off. Clever idea.... also rotten idea!

Anything else to consider? If not will get it back together and see how she blows....
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Old 10-23-2016, 02:25 PM
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Sounds like you found enough that would cause your issue(s).

The hot start issues made me think of a coil/ignition issue - I would also check a few things on the ignition...

- check the coil.
- check spark plug wire to make sure it is "well connected to coil".
- check grounds - make sure good contact to frame, etc.
- visually inspect the kill button wire to make sure no chafing.

jeff
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Old 10-24-2016, 05:18 AM
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Thanks Jeff - bike is still in bits with easy access to those parts so will give it a try and see how it goes.


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  #7  
Old 10-25-2016, 01:06 PM
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Checked all the electrical connectors as well.... all ok. The only thing I noticed at the weekend was that the screw on the tip of the plug was also loose.

Time to get the thing back together.....

Are the jet sizes marked on the edge of the carb jets?

Worth noting them down before I box it back up.


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  #8  
Old 10-25-2016, 03:58 PM
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Been out in the garage again tonight, sure my neighbours must love me....! Here are my findings.....

Gas Gas - Dellorto 26 PHBL Carb Details:

Pilot Jet- 35
Choke Jet - 60
Main Jet - 270K
Float Needle - INC (Red tip - no numbers)
Float Jet - 200
Slide - 60
Needle - D36
Clip - 3/4

Idle Screw = ??
Air/Fuel Screw = ??

Starting from cold in garage (at ~25-30'C ambient, 50-70% RH, close to sea level), then latterly after running for a few mins and repeated starts, bike seems to favour choke + 1/2 to cracked wide open throttle to start, otherwise just splutters.

Bike still not easy to start but now more likely to get it fired up with right twist/prod, etc.

Plug cleaned and re-gapped but probably would benefit from a fresh plug.

Didn't note idle & A/F screw positions but A/F responsive to 1/4 turn. Idle screw, responding over wider range.

Questions:

What are the base jetting and screw settings?

Where can you find jetting tables?


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  #9  
Old 10-25-2016, 06:35 PM
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Grab a few beers and watch this from Jim Snell.

https://www.youtube.com/watch?v=QT7XK4123hI

Jim would be more than happy to help you out if you email him he knows more about GG trials bikes than anyone on the plaint.
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  #10  
Old 10-26-2016, 12:29 AM
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That's spot on..... thanks cbutler


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