2004 GTI Blown pistons with pics, diagnose problem

[joaquin12345]

So I got this from some friends that used to ride with me. I always brought my 2 94 xp's 657x ski's and they always brought there 2004 GTI which they had got from a public sale. The ski ran good they first started bringing it but being a mechanic the owner always tinkered with the ski trying to get it to run faster then mine, which never happened. Anyways he played around with the single carb but it never really ran good enough. The last time out it ran really well and he was happy but after about 10min on it and a wot stretch of about 100yards it died. I pulled him back in took ski home, we took off head and noticed the rings on the front cylinder, (dont know correct term), was chewed up. They ended up selling me the ski as a trade for a trailer I paid $300 for. Today I took cylcinders and pistons off and shipped to full bore for a new top end kit and boring of cylinders. I sent the pistons so they could diagnose what happened but I figured the guys on this site might know a little more.

Questions:
1. What could have caused this?? Does it look like no oil or carb issues??
2. Do I need a new head and does anyone have one?
3. Fullbore the right place to go with?
4. Do the rings look like they actually fit?I know this thing was done previously as the pistons said sbt on bottom?

 

[ocod]

Looks like two different pistons...
:banghead:

Pm 99spxxx or minnetontaka4me for new head
may cost same as fixing old one if it could be done.

 

[joaquin12345]

Here are the rest of the pics. It wouldnt let me download all at once

 

[ocod]

Cheap sbt parts.

Buy oem or prox pistons on next rebuild.

 

[bell99man]

Hey, SBT offers a 2 yr warranty on some, so not all junk butI'd be looking at plugs for detonation. If you look around this site you'll find 2 cycle fuel and carb issues all over it. But, for $300 bucks you can't go wrong. Buy it a new engine or heck, even just a top end with a good tune up will get you lots of fun. Check those fuel lines (gray is bad), and install an inline fuel filter about 2 ft from the carb.

 

[ocod]

Hey, SBT offers a 2 yr warranty on some, so not all junk butI'd be looking at plugs for detonation. If you look around this site you'll find 2 cycle fuel and carb issues all over it. But, for $300 bucks you can't go wrong. Buy it a new engine or heck, even just a top end with a good tune up will get you lots of fun. Check those fuel lines (gray is bad), and install an inline fuel filter about 2 ft from the carb.

On a complete engine.

Makes you wonder what happened the first time?

Its a quality issue that I rather not skimp.
I like OEM things for certain things.
Especially if working at 7000k rpms.

 

[mikidymac]

With the condition of that piston I would question the condition of the crank. It is not likely the crank would survive the forces as well as the debris that went thorugh that cylinder. Also check the rotary valve and it's shaft/gear. If I had to guess I would say either a mechanical defect or you lost oil to that cylinder because it is a single carb and the rear looks fine so they were getting good fuel.

 

[bell99man]

Missed that...yep, get a new engine.

 

[Dr Honda]

Cheap sbt parts.

Buy oem or prox pistons on next rebuild.

Please don't bash SBT. I've used a bunch of their parts/engines... and never had an issue.


With that said... I'm looking at rust in the one cyl... so I'm going to assume that the problem wasn't from parts quality. I'm 100% sure it was from user error.

Basically... when the engine has to polish away rust... the engine normally will just east itself.

 

[riding high]

So I got this from some friends that used to ride with me. I always brought my 2 94 xp's 657x ski's and they always brought there 2004 GTI which they had got from a public sale. The ski ran good they first started bringing it but being a mechanic the owner always tinkered with the ski trying to get it to run faster then mine, which never happened. Anyways he played around with the single carb but it never really ran good enough. The last time out it ran really well and he was happy but after about 10min on it and a wot stretch of about 100yards it died. I pulled him back in took ski home, we took off head and noticed the rings on the front cylinder, (dont know correct term), was chewed up. They ended up selling me the ski as a trade for a trailer I paid $300 for. Today I took cylcinders and pistons off and shipped to full bore for a new top end kit and boring of cylinders. I sent the pistons so they could diagnose what happened but I figured the guys on this site might know a little more.

Questions:
1. What could have caused this?? Does it look like no oil or carb issues??
2. Do I need a new head and does anyone have one?
3. Fullbore the right place to go with?
4. Do the rings look like they actually fit?I know this thing was done previously as the pistons said sbt on bottom?

I will throw my 2 cents worth in just for the record. NOTE; All standard disclaimers apply.

In my most humble opinion the problem was caused by detonation. However I will always defer to Doc's opinion. I only say this because I just finished rebuilding a 787 engine and it looked just about like your's except the piston actually had a hole in it. If you have the grey fuel lines on your unit you will definitely need to replace them, install an in line filter, and have the carbs rebuilt. NOTE. These carbs are not your normal animals and do require some special tools. I recommend that you consider sending them to Doc to get them rebuilt.

My head looked as bad as yours or maybe even worse. I was going to get a new one from those on here that have already been mentioned. I took it to a mechanic friend of mine and he polished it up and it looked pretty good to me. I also took the head to the local SeaDoo dealer to get his opinion. He said that they use head's in that condition all the time if it is just for recreational use but it would not qualify for a racing machine. We will see and I pray that it is OK.

I used FULL BORE and was completely satisfied with there work. Dan puts out quality work and the ring end gap will be within spec.

If you haven't done it yet I would suggest you download the manual and read it.

You will need some additional sealant's if you don't already have them.

Also, I did inspect the crank full well expecting it to be shot, but for some reason it was good to go. Heck even the rod was OK.

There is a lot of good knowledgeable people on this forum and they are willing to help you. Please let me know if I can be of any assistance to you.atriot:

If you do the engine yourself be sure that the rave valves are ground. If you sent them to Full Bore Dan will take care of them, if your engine even has them.

 

[ocod]

Please don't bash SBT. I've used a bunch of their parts/engines... and never had an issue.


With that said... I'm looking at rust in the one cyl... so I'm going to assume that the problem wasn't from parts quality. I'm 100% sure it was from user error.

Basically... when the engine has to polish away rust... the engine normally will just east itself.

I'm not bashing. I'm just saying.
Looks like OP PO put a band aid and took the inexpensive way out.

How many times do we tell people about the failure of not figuring out root of initial failure to avoid where the OP is now. Looks like other piston is involved. Not that OP would know that.

I would use and recommend people use SBT if they get a whole engine.
That way they are covered.
But for top end leaving a stock bottom end I would use OEM or PROX.

But yes his problem was engine ran lean b/c there is something wrong with the fuel / oil / air.