04-10-2011, 08:29 PM #1
97 gp1200 - Possible blown engine?
Well, if this the worst time to happen - start of season!
LAST season, it would hesitate to take the gas unless you opened it slowly.....
Today I tested the compression, on the back cylnd. and it was 90, the other two, 120.
I knew this was kinda low, obviously.... Started it up, it back fired, died, restarted and ran good out of water.
I put it on the water, it hesitated a little and then ran perfect. I get about 10 miles from the ramp ( luckily with a friend!!! ) and it cuts down and then dies. I spent 3 hrs towing with a crappy rope that kept breaking, but got it in finally!!
NOW, its gotta knock going on, does any one have any ideas? I just got it home and havent had a chance to start tearing it down yet..... what shall I look for to determine whats wrong with it?
( A new top end was put in last year around march, when I bought it )
I did try searching, yes! THANKS!
04-10-2011, 09:59 PM #2
do another compression check and then you can figure it out from there
04-10-2011, 10:15 PM #3
- Join Date
- Oct 2005
did I read this correctly? you knew it had low comp and then went out riding?
knocking could be a few things... you already know one cylinder is low, so yank the head and have a look...
is it the original crank?
04-11-2011, 12:46 AM #4
The compression was low, but really wasnt sure if it was an issue, @ that number. I took it out mainly to run it for a test, and to see how it was going to behave... since it had the hesitation in it at the end of last season.
I assume the crank is the original, the guy said he just rebuilt the top end ( Im not exactly sure what all that includes myself, can some please advise on that as well ? )
04-11-2011, 09:26 AM #5
- Join Date
- Jul 2005
- Central North Carolina
04-11-2011, 10:52 PM #6
Hi, Thanks for the info so far - Premix only and usually pretty rich more than 40:1
Im thinking where its probably not had a carb rebuild and the hesitation it gave me near the end of last season it was causing the back piston to run lean, and then sitting this winter just made it worse, till it took it out today... anyone think thats possible?
I havent made it to tear it down yet, hoping to soon for sure.
I didnt get to run any of the water out of it like usual when done riding, will it cause more probs?
04-12-2011, 02:33 PM #7
Some info from the guy I got it from last May.
It had 74.3 hrs on it. All he did was hone the cylinders and rering them. Each cylinder had 120 psi.
Ok so, guess if I am rebuilding, what all should be replaced?
And wheres a good place to start for the parts?
04-12-2011, 11:02 PM #8
Its possible it injested some water into the engine by towing it 10 miles. If so, it needs to be disassembled immediately or your crank is gonna rust up. you might need a crank anyways if its knocking.
Buying a new crank is like $900 I think. Having your current crank rebuilt might cost about $400 to $500.
Buy a complete engine gasket kit. I recommend OEM Yamaha stuff here. About $200
Sounds like you're gonna have to rebore at least one cylinder. Its a good idea to do all 3 at once. So you're looking at new pistons and rings. 3 ProX piston kits (with rings) are gonna cost about $280
Bore and Hone about $250 to $300 maybe.
3 carb rebuild kits about $150
Stuff is adding up fast isn't it.....
04-12-2011, 11:09 PM #9
Thanks again for that info - def getting it apart tomorrow.
I've got the carb kit already, thank god as yes, it is adding up. Might just jerk the motor outta the 99 and put it in the 97, I like it better. And part the rest out, prob be better off and may make a $ in the process!
I did speak more in detail to the guy who used to have it. He used SBT parts, wonder ( with all the complaints Ive seen here ) if that's not the issue. I wouldn't think, but obviously knowing EXACTLY what caused the issue to begin with will help make sure that wont happen again!
04-13-2011, 02:58 PM #10
Well, here's some pics... everything seems to still move fine, which is def good. I guess.
Any thoughts on the best, most cost effective way to take care of this and the best place to grab the parts from ?
There's some damage to the head, but very little. The sleeve is scared up, dont think a honing will fix that for sure. The piston is F'd obviously.
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