Blew right piston on GT185, don't know why.

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vman858
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Suzuki 2-Strokes: GT185 Ulysses KLR TW CRF

Blew right piston on GT185, don't know why.

Post by vman858 »

I run a charity race around Lake Erie, 650 miles, 12 hours pretty much wide open, only stopping for fuel. I have a extra 2 gallon tank mounted on rear that I turn on when I hit reserve on main tank. This is my third year on this bike, but this year I had new crank seals installed, bored 1.00 mm over with new pistons rings etc. Did a pressure check and holds 5psi all day long, compression 135psi. I got it put together and did the break in and ran about 200 miles prior to race. The bike is stock except the 1.00 mm over bore and no packing in the stock pipes. Stock air filter with stock jetting.

Well I'm flying along I90 at about 7k rpm in 5th gear and this baby is kicking butt. Then I get that bow bow bow of no fuel and reach back and turn on the rear tank. After a bit nothing, so I turn main to reserve and I start making power again. After about 30 seconds turn off main tank reserve and give rear tank another try. Same thing, runs fuel out of lines then bow bow bow. Main tank reserve on and making power. I go through this a few time and then something changed and I can tell somethings not right. Pull over and discover rear tank fuel filter is air locked. I pull right plug and its covered in aluminum and no compression on my thumb over plug hole.

All you experienced 2-stroke guys... Could this fuel scenario of switching back and forth cause my lean condition? Anyone ever hear of this? I am new to 2-strokes and looking for some advice.

Thanks
Vince
rngdng
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Re: Blew right piston on GT185, don't know why.

Post by rngdng »

Well, maybe. Obviously it goes lean as the tank runs low, and you shift to reserve. Whether that happening a few times in a row would blow it up, I don't know. It wasn't a good thing, though. Sorry to hear about it.



Lane
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Zunspec4
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Re: Blew right piston on GT185, don't know why.

Post by Zunspec4 »

Hello Vince,

With the banzai running you were doing (sounds like a bunch of fun :up: ) the engine would be fairly hot and if you then basically had fuel starvation you can easily hole a piston in a trice. This can happen even if all the various adjustments are spot on. Been there and done that :lol:

Cheers Geoff
GTandcbr
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Re: Blew right piston on GT185, don't know why.

Post by GTandcbr »

Petrol in the mixture not only provides the explosion but also cools the vapour to prevent it becoming unstable and overheating the piston crown. No petrol fed into the cylinder for a period of time means a combination of red hot plug that therefore holes the piston. This happened to me on a 550 when the petcock stuck closed with the same result.
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Flywheel
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Suzuki 2-Strokes: 1974 GT185
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Re: Blew right piston on GT185, don't know why.

Post by Flywheel »

If there is any obstruction or sediment in either petcock restricting the volume of flow, the right carb is going to be the first to be starved of fuel on the GT185. This is due to the slightly longer travel path for the gas to travel to the right carb (at least with the stock tank).
vman858
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Suzuki 2-Strokes: GT185 Ulysses KLR TW CRF

Re: Blew right piston on GT185, don't know why.

Post by vman858 »

Thanks for the info guys. Sound like that's was it. Yes the ride is a blast. I invite anyone here to come join us next June for a great ride and great people.
vman858
On the street
Posts: 11
Joined: Wed Mar 11, 2015 8:11 pm
Country: USA
Suzuki 2-Strokes: GT185 Ulysses KLR TW CRF

Re: Blew right piston on GT185, don't know why.

Post by vman858 »

Ok finally got new piston in. It's running good, but old piston was 4oz with rings and pin and new non oem is 3 3/4 oz. Definitely not ideal. I'll keep up guys updated. Race in June!! We are having a dedicated chase vehicle for all racers this year so come join the fun,food, and drink....Google lake Erie loop race.
Vintageman
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Re: Blew right piston on GT185, don't know why.

Post by Vintageman »

How did the piston fail (hole in top center).

If you going to run it straight out like that again.

Warm it up then switch to a couple step cooler plug
run one size or two up on main jet for cooling and allow a little extra oil mixture in tank (50 -100:1)
keep the fuel topped up. higher octane gas is wise too

I had a gt185 hopped it up a little and just could not shed heat be it air cooled design. cooler, plug a little rich and extra lube, prevented me from holing piston... but gain it is just air cooled and not sure it can run 100% duty like that... may want to add some side air scoops directed towards cyl and head fins for added cooling.

Sound like it was a fun ride! try again!
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