Home. Back. ...... The Gas Gas Guru. Technical Information.

As part of an inheritance from my father, I recently came into possession of
a mint-condition 1997 JTX 270. My problem is that I just cannot get the thing to start, much less even try to. In my trouble-shooting process, I have made some common-sense moves, like:

-making sure the fuel is turned on

-making sure that the fuel line is connected and is not clogged

-making sure the plug is connected, gapped correctly, and is making a spark.

I observed that fuel appears to have gotten to the float bowl. Although, when I remove the plug, it appears dry, and does not smell as if any fuel has reached it. Besides helping me solve this problem, could you give me some everyday tips for starting this motorcycle? The manual is not much help.

Thanks for your time!!!



My first guess is that the bike has been stored for a little time and the jets are clogged. Take the carb apart and remove the jets and clean out the orfices with a sharpened toothpick. Cleaning them out with wire might enlarge them or change the flow pattern. Blow out all the passageways with compressed air. Remove all old gas from the tank and lines and replace with a mixture of 70% Preminum pump and 30% hi-octane unleaded race gas (Gas-Gas recommends 95 octane fuel and most pump gas is 93 octane at max) and an 80:1 premix oil, full synthetic.

Gap the plug, NGK BPR5EV or equivilent, at .024".

The "choke" lever is that black lever on top of the carb and may be hard to reach. Put it straight up, which opens the enrichening circuit. It will be harder to reach when you want to turn it down after warm-up and most riders drill a small hole in the end of the lever and attach a ziptie so they can grasp it with gloves on. Leave the throttle off, push down on the kickstart with your boot (wear boots!) until it starts to engage and THEN put your weight into it. After two kicks, if it already hasn't started, crack the throttle a little while kicking.

A lot of riders just stab at the kickstart without taking up the slack in the engagement system and this leads to broken levers and gears in any bike. Give this a try and let me know if you have any further problems, I'll be glad to help.




Thanks for the help!

I did what you suggested. Upon reflection, I do think now that the real problem was that the choke was never actually flipped all the way up.Now,
the bike starts up with 2 or 3 kicks on the choke, but the engine seems to race. I suspect that in taking the carburetor apart, I may have thrown the needle and/or the mixture screws out of adjustment. Can you tell me good starting points for adjusting these items? As well, I assume there is a shop manual for this model (the owners manual isn't very helpful). Can you direct me to it, or do you think that necessary? Kit


A high idle with the "choke" on is normal. That lever isn't for an actual choke, but actually opens up a small orifice (or a secondary venturi) on the side of the main venturi, where a richer than normal amount of fuel is added so the engine is getting more air and fuel than supplied by the slide/venturi system. It should go back to normal when the "choke" is shut off.

The needle will not be out of adjustment. And unless changed, the float level will be the same. The mixture screw (or in the case of the JTX, I think it's an air adjustment screw) can be initially set at 1 1/2 turns out from being LIGHTLY seated. It's critical to only turn adjustment screws (on carbs, shocks or forks) in until they are lightly bottomed out. I get a LOT of questions concerning broken adjustment screws from them being forced in. They are fragile and a light touch is always needed. Start the engine and let it warm up. Then turn the screw out until the RPM's remain steady then adjust it 1/8th turn in. That should do it. Sometimes the screw needs to be turned out or in a little to give a clean response to the throttle. Blip the throttle just off idle to check, as the mixture adjustment screw has an effect on off idle response. It's not unusual to see the Pro's adjusting their carbs in the middle of a Trial, due to atmospheric changes, to get that last bit of smooth response from their bikes. This all takes a little experience and practice as the engine responses are subtle but you'll get the hang of it in a short time.

I'm not aware of a hardcopy shop manual available to the public. Your bike should have come with the excellent video manual done by Jim Snell of Rising Sun Imports, did you get one? Feel free to contact me with anything I can help you with.


Professional tuner and 'Trials Competition' writer Jon Stoodley has very kindly stepped up to the plate to answer your questions. If you're having problems, or need some advice just send an email to Jon. If it's something that could be useful to others, we'll post it on the site.
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