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Boiling Gas

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I had a strange occurance today that I would like to share. I have a 2005 DRZ S with a Clarke oversize gas tank. The bike has low miles and service done in accordance with the Suzuki Service Manual. I took the bike to Red River Motorcycle Trails at Bulcher, TX, (Red Bull Last Man Standing 2006-08), and did a ride over the enduro course that was layed out for last weekend's race. About 10 miles down the course I noticed my bike starting to run a little rough going up some of the hills. This finally turned into being a chore just trying to keep it running. I could smell raw gas but saw no sign of a leak, so I decided to give her a rest and give everything a good looking over. The fan was running as it usually does, but instead of cycling quickly it continued for some time. Obviously the bike was quite hot but I couldn't find any fuel leak, and the motor turned over freely, it just didn't want to run worth a crap. My son unscrewed the fuel cap and the pressure from inside the tank blew the cap right out of his hand. The gas was literally rolling in the tank just like it was near boiling temp. It got so hot the opening in the gas cap couldn't relieve the pressure quick enough. I think the pressure built up so high that it forced gas past the needle and overflowed the carb bowl and resulted in a rich mixture, thus flooding the engine and causing the stalls. Once the bike cooled off, all was good and I continued on for the rest of the afternoon with no reoccurance. Coolant was changed last year and replaced with Liquid Ice, and a check of water level at the end of the day showed no drop in the coolant level. My riding buddy was a service manage for Kawasaki for 12 years, and he had never heard of such a thing, but agreed with my assessment.

Not looking for a fix, just sharing.

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Well, of course that happened to Dungey this year in I believe Texas. But if memory serves me right it 100 degrees that day, and of course the motor was under race conditions. I think the first thing I would do is get a vented cap. Next, is there Ethanol in the gas in Texas? Here in Missouri it's a problem with the ethanol swelling the plastic's, be it tanks or gas caps. I've seen this problem on weed eaters, chain saws, and my Clarke gas cap. Not that we can do it with our bikes, but, say with chain saws, leave the cap off for a couple months and it will screw right back on. Where before you couldn't even force it back on. Just a thought. Cman.

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The ambient temp did get up to the upper 70s, and we were riding pretty hard through deep ravines and steep hills, so there wasn't much air circulation. This was the first time riding the DRZ this hard with the temps this high. I usually reserve these conditions for my KDX, but my son wanted to ride and I let him have the lighter of the two. The Clarke gas cap is vented with, what I would guess to be, an 1/8th in. hole. I think the nipple is thick enough I can drill it out to 7/32, but at the rate I observed the vapors escaping with the cap off, I doubt this would be enough, but nothing ventured, nothing gained. I wish I had a video of the gas rolling in the tank when we first opened it up. My son and I couldn't believe what we were seeing.

I have seen what ethanol blend can do to plastics. Not pretty! I went through 2 gas tanks on my Toro mower before they figured it out. In Texas premium gas has no ethanol, so I spend the extra pennies per gallon for peace of mind.

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I'll have to check my Clarke but isn't it a one way vent?

I have heard of guys having this problem but I have never experienced it. I ride mine year round and that includes 110+F commutes (parks?) on I35 and I've never had a problem. I did see a post at one point where a guy put the exhaust type heat shield on the tank and that fixed it.

Hopefully I can get up there in the next couple weeks. I'll try to replicate it!

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I did see a post at one point where a guy put the exhaust type heat shield on the tank and that fixed it.

Hopefully I can get up there in the next couple weeks. I'll try to replicate it!

If it happens again that will be my plan of attack.

I will be there Saturday after next as well. Keep you posted and maybe we can meet.

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I had this exact thing happen to me back in May during a poker run in Rampart Range. It was a "enduro/hare scramble" type of event, at or around 9000 ft., probably near 80F or better for about 60 miles of trails. Bike started acting weird, had to give it throttle at times just to keep it from stalling. Thought I had run out of gas, unscrewed the gas cap and it proceeded to act like nothing else I can describe other than a teetering weights on a pressure cooker.

I don't think it's much of a big deal but I will be installing a manual fan switch this winter. I am new to dirt riding and tend to ride pretty slow, so that day the radiators didn't really get a chance to do their job.

But that was 5-6 months ago and have graduated from 1st gear to 2nd for general trail riding. Don't know how fast you ride, but that makes a big difference. :lol:

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If it happens again that will be my plan of attack.

I will be there Saturday after next as well. Keep you posted and maybe we can meet.

Might be doable.

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