2001 GP1200R rear cyl seizure problem. (2nd time)

[geraban19]

Gera,
You need to pressure test that engine. Basically it needs to be air-leak tight. If not, you will burn a 3rd piston and cylinder.

To do this, you will need to reassembly the cylinders and head. Block off the exhaust, intake and pressure the engine to 10psi. If it leaks down to 0psi, then find the leak and repair. This is not easy to do with engine in ski. You might consider removing engine to do this.

Mark, the engine is OUT of the ski.
I never did tis kind of test and I guess I need a vaccum pump instead a pop off gauge correct?

Gera

[geraban19]

Gera,
You need to pressure test that engine. Basically it needs to be air-leak tight. If not, you will burn a 3rd piston and cylinder.

To do this, you will need to reassembly the cylinders and head. Block off the exhaust, intake and pressure the engine to 10psi. If it leaks down to 0psi, then find the leak and repair. This is not easy to do with engine in ski. You might consider removing engine to do this.

Mark, the engine is OUT of the ski.
I never did tis kind of test and I guess I need a vaccum pump instead a pop off gauge correct?

Gera

Never mind.

I will get this stuff to test my engine.

Now I am more happy since I have an start point input from experient guys.

Thanks a lot. I will post feedback during assembling checks.

Gera

[Hydrotoys]

Some more ideas to make your block off gaskets.

[Hydrotoys]

I made my gauge out of a tire guage, a brass tee, 3/8 hose clamps, a spare tire nipple to add air and a quick connect to my old compression gauge... The red rubber is from the hardware store.

Use soap and water in a spray bottle to look for leaks. Don't go over 15psi.

[geraban19]

I made my gauge out of a tire guage, a brass tee, 3/8 hose clamps, a spare tire nipple to add air and a quick connect to my old compression gauge... The red rubber is from the hardware store.

Use soap and water in a spray bottle to look for leaks. Don't go over 15psi.

Very smart... now I understand each part.

What I noticed from your pics and Fernando's was that he injected air in one of the pulse fittings and also isolate the carb pumps. In your case U injected in the spark plug hole and also plugged all 3 pulse fittings to each carb pump. correct??? So I don't need to isolate fuel pumps?? Can I inject air at any place?

A compression gauge won't do the job?

Gera

[Hydrotoys]

It doesn't really matter... as long as you dont fill it too fast. Remember some air will bleed past the rings, up into the cylinder cavity as you are filling.

It is probably better to isolate the fuel pumps from this process. It would be bad to blow out a fuel pump trying to isolate another problem!!!

[mile_hi_1300]

Hey guys, for what it's worth, My XLT1200 (99) popped it's #3 when it was reassembled at the dealer's shop and the monkey's overtightened the carb plate. It cracked ant that's where mine leaked at. Just a thought.

[Fercho]

I would isolate the fuel pumps. Dont go over 10 SPi on the pressure test. If you use red gasket material 10 PSi will stretch the heck out of it. I usualy double the gasket. Seen how bad the gasket is strached with 10 PSI, its possible that this will damage the fuel pump diaprhgm if you connect the hoses. DONT DO IT THAT WAY, REGARDLESS IF SOMEONE ELSE DID NOT HAVE ANY PROBLEMS YOU ARE TAKING A BIG CHANCE IN DAMAGING THE PUMPS, AND IF THAT HAPPENS YOU WILL SEIZE AGAIN.

Disassemble your carbs and check the entire circuit for debris and inspect all of your o-rings and check valves. I would highly recommend to drill out the built in return fuel restrictor on the body of the carbs and use a 90 main jet on the return line, this way all 3 pumps work together and the pressure is equalized.

I got my gauge years ago from GroupK.

[geraban19]

Disassemble your carbs and check the entire circuit for debris and inspect all of your o-rings and check valves. I would highly recommend to drill out the built in return fuel restrictor on the body of the carbs and use a 90 main jet on the return line, this way all 3 pumps work together and the pressure is equalized.

U mean open the hole completelly???

I actually running #120 main jet in the return line and after do this I solved my low end problwms.

Gera

[Hydrotoys]

Fernando's right about those fuel pumps.
Also he posted this in another post about pressure testing. I thought in your situation, this would be a smart thing to do to.

My recommendation on the single pipe is to bolt up the exhaust manifold in place accordingly and make a round blockoff gasket that goes between the exhaust manifold and the head pipe. There have been numerous report of engines that seized because of water intrusion due to ckack exhaust manifolds,. This is the time to test it.

[geraban19]

Guys,

I just talked a couple of minutes with my mechanic by the phone about this problem because we are going to rebuild it tomorrow.

He has been out of all this conversation and has telling me that he was going to make a meticulous analysis.

Today he just told me his opinion and I want to share it with U experient guys. First of all I want to say that he is a 25years of experience motocycle mechanic and I give him a lot of credit.

Here's his diagnostic WHITOUT ANALYSIS the whole engine.... He based it from the repetition of the problem and just looking at the damaged piston. He didn't worked assembling this engine at the prior times because it was treated as an OEM engine that is responsability of other mechanics of the shop.... he takes care of my race skis.

He said:

- Did U noticed that the damaged in the piston is located at the side of the piston not at the front and rear face (intake and exh sides)??

- Did U noticed that the problem occured on the top of the piston where it is smaller in diameter??? (I know that it is higher temperature area)

- Aren't U thinking that the rear rod (#3 cyl damaged) can be not aligned very well??? Even too much tight or located too back or too front???

- There's no wear to the other cylinder and the one that had a seizure had been replated. So, if it dilatate and seizure why it choosed one of the sides to do it more???

- Can be a rear bearing or even a bad rebuild crank be the problem??


What U think guys???? I am really excited to go there tomorrow and find out.

Gera

[Hydrotoys]

- Did U noticed that the damaged in the piston is located at the side of the piston not at the front and rear face (intake and exh sides)??

If he is a good mechanic, then when he see's the cylinder and piston together he should KNOW that the damage will always be on the sides with a siezure. The intake and exhaust is not front/back. This is why I avoid motorcycle mechanics.

- Did U noticed that the problem occured on the top of the piston where it is smaller in diameter??? (I know that it is higher temperature area)

No, the problem is those huge freakin deep scratches down the sides and the stuck/broken rings.

- Aren't U thinking that the rear rod (#3 cyl damaged) can be not aligned very well??? Even too much tight or located too back or too front???

The rod aligned very well??? A two stroke mechanic with a knowledge of a pressed crank SAID this?

- There's no wear to the other cylinder and the one that had a seizure had been replated. So, if it dilatate and seizure why it choosed one of the sides to do it more???

Because any two stroke mechanic with knowledge of crank seals, labryth seals, intake/exhaust charge, and engine leaks would know that you can not diagnose a problem like this by guessing about why one cylinder baked itself and the others didnt

- Can be a rear bearing or even a bad rebuild crank be the problem??

Yeah sure, but a rear bearing should have released hard metal pieces into the piston/cylinder and ate up the cylinder head and piston top with ring-shaped divits and missing chuncks. If the rear cylinder has ingested water, you can spin a journal throwing timing off in the rear cylinder, and cause damage. You can also bend a rod this way. Both of these items could easily and quickly be checked, with the crankshaft in the engine, as long as you have the piston and cylinder.

**If your mechanic does not want to pressure test your engine before tear down, then quickly get all your stuff gathered up and run away**

[geraban19]

I better shut up my mouth...

ehehehh

Lets see what we found....

I really want to see a bad fuel pump in the rear carb.


Thanks

Gera

[Hydrotoys]

No,
everything is fine.

But dont let this single cylinder motorcycle mechanic smooth talk you into doing something that you DONT need, when you have been provided tons of info here, and could have already figured out some important data.

Knowledge is power. Power is speed.

[geraban19]

Guys,

I just replaced my bad cyl and increased the main jet from 125 to 135 and set the adjustera like 1 turn, 1 turn and 1 1/2 turn (pto, center, mag) and I had no seizure problems. Pilot jet is #110.

Brazziliam pump gas is too bad guys.

My boat now has a very strong low to mid acceleration and a poor 62-63 mph top speed. Is it really slow for a GP12R stock with out acc pump and a solas prop?


Gera