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Trail-riding Meltdown - Is Race Gas The Answer?


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#1 farmerj

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Posted 17 March 2012 - 04:08 AM

I was trail riding up in the mountains with my '01 txt 321, trying to keep up with my buddy on his DE 300 - and my bike got so hot that we started smelling something burning. We thought it was a problem with electrical wires. Turns out that the middle muffler area got so hot that it melted a hole in the brake fluid reservoir :o

Why did this thing get so hot? Was it from an elevation change that affected the jetting? Middle muffler clogged? Just pushing it too hard?

Fan and water levels appear OK. I was running the gas/oil mixture at 80:1.

My dealer said that he often has problems with overheating when trail riding a trials bike. His solution is to run Race gas and a 40:1 gas/oil mixture.

(1) Will that work? Does Race gas run cooler?
(2) Is there any problem with running Race gas in a (stock) trials bike?
(3) Do I have to re-jet for the 40:1 mixture?

Thanks! I don't want to burn something up again!

Jeff


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#2 copemech

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Posted 17 March 2012 - 04:49 AM

I think you are going to get varying opinions here, but if the bike is running otherwise normally, I would not be inclined to change a lot of things.

Some insulation between exhaust and res would be good. Insure ignition timing is not set back too far on the stator plate, as this will lead to excess heat in the exhaust due to short burn period.

I do not neccessarily think that a higher octane of race fuel will keep your exhaust cooler under high load conditions, nor am I a proponent for a 40:1 mix of oil unless you are roadracing the thing, you might go to 70:1 for hard use(full synth).

Jon may have other thoughts on the EGT situation using a higher octane fuels than needed, as I have no specs, yet seems may be counter productive.
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#3 lineaway

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Posted 17 March 2012 - 01:15 PM

The middle box probably had years of unburned oil in it. When pushed harder than it ever has it started burning within. And yes modern trials machines are not made to run this hard. Jetting for trail riding is totally different than for trials. I`d go up several sizes on the main jet and at least a 38-40 on the pilot. Nothing wrong with 40-50:1 with good oil if you are climbing steep trails. Remember your radiator only pushes out, does not have an over flow or recovery type system. You also have to watch your brakes. In trials we tend to keep them `tight` for instant response. Have seen many a brake over heat and a few actually catch fire on a long ride in the mountains.Never been a fan of race gas in an engine ment to go slow.

#4 thats_a_five

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Posted 17 March 2012 - 03:43 PM

Just for reference to riders from other parts of the world, yesterday in Oregon it was probably only about 45 degrees F (7C) and there can be a lot of elevation change riding the mountains nearby. What sort of trails were you riding? Tight, twisties or fast quad type uphills and fireroads? I suspect high speed, high RPM. Did the bike seem to be smoking more than usual?

I would tend to agree with Lineaway on this about the center muffler box. I recently did some work on mine in my '94 JT25 (see other thread about this). When I took the box off it was completely black inside from years of accumulation. I could not even find any of the perforations in the inner baffle because they were clogged with gunk. I soaked it in diesel fuel for a day then burned it out. WIth my propane torch in one end, it got hot enough inside to burn off all the oily residue and it was like a blast furnace shooting out the other end. And lots of oily smoke. I could only imagine if this got hot enough to ignite when riding it would potentially burn the bike down! When I got done I could see all the perforations in the inner tube very clearly. Just a caution - my muffler is steel - if yours is aluminum I would not recommend getting it quite as hot as I did.

I also replaced my old air filter that was pretty bad, making the bike run rich. I have not had the bike on a real ride since I did this but just around the yard the bike seems to run smoother and have more zip on throttle. Plus I feel a lot better that I will not have roasted nuts after a long ride!

#5 farmerj

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Posted 17 March 2012 - 04:43 PM

Just for reference to riders from other parts of the world, yesterday in Oregon it was probably only about 45 degrees F (7C) and there can be a lot of elevation change riding the mountains nearby. What sort of trails were you riding? Tight, twisties or fast quad type uphills and fireroads? I suspect high speed, high RPM. Did the bike seem to be smoking more than usual?


This actually happened last fall. It was 80 degrees F, 3,000-4,000 ft. elevation, 3rd gear twisty trails through the trees. The bike seemed to be running "funny," not as smooth and a little down on power. Seemed to be running rich. Usually I'm at 500' elevation. Yes, I was pushing it - but I didn't feel it was much more than at other times. At one point it died - I thought I had seized it - but it started back up fine and I rode back to the staging area.

I'll search for some posts on middle muffler cleaning. This one can't be taken apart! I've heard of guys cutting them open, then re-welding - which I can understand, given a new one costs something like $500!

Jetting was 36 pilot, 114 Main, D36 needle.

Thanks for your comments, those are helpful!

Jeff

#6 thats_a_five

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Posted 18 March 2012 - 06:33 AM

My center muffler can not be disassembled either. I took it off the bike, soaked it and burned it out. Did not cut any access holes or attempt to replace the packing. Just burned it out and reinstalled on the bike.

I have not see any posts on the Gas Gas forum other than mine but I have seen several on the Montesa forum.




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