91 xp pto cylinder

[Jetman454]

I have just rebuilt the entire engine and carbs on a 1991 xp. First trip to the lake found the pto cylinder running very hot. Runs hot on trailer (yes the ski was in the water)at idle and just above. Never even took it off trailer. My question is will too high of a pop off pressure lean out the pto carb (mag carb using the available pressure and starving the pto)? I used the seadoo source which calls for 21-37psi. Manual calls for 21-25. Mine are at 30/31. LS is 1 1/2 and HS is 1/4.

 

[mikidymac]

You need to make sure you are using the correct Genuine Mikuni parts.

1 psi difference will make no difference and neither cylinder should be noticeably hotter than the other.

 

[Jetman454]

Everything is Mikuni parts. I'm actually about 6-7 psi different from the manual numbers. Right in the middle on the seadoo source numbers. I've checked the cooling system, all is well there. I'm setting up for another pressure check of the block. Was good when I installed the motor. Have lighter springs coming. If leak down check is good, all I can figure is pop off is too high. I'll look at jets again too make sure they didn't clog up. Have brand new lines, tank was removed and cleaned too.

 

[mikidymac]

What do you mean "lighter springs"?
1991 XP should have 95 gram springs period.

 

[Jetman454]

I put what came in the kit, which is 115g springs. Which put me at 30/31. Like a dummy I threw the originals out by accident. I have the 95g coming to put pressure more inline with what the manual says not seadoo source.

 

[Jetman454]

I'm doing the leak down again because I had a mix up with flywheels. I put a 7091 on instead of the 7001 and took a pretty bad backfire. Hoping its just a carb issue but I have my suspicions I may have inadvertently blown out a seal somewhere.

 

[Jetman454]

So leak down test shows a small leak. Like .5 lbs for 5 minute. But if I rotate the crank it doesn't leak at all. Dont know what would cause it to leak in one position and not another. No high spots on crank. Runout on reworked crank was .0015. New oem seals installed.

 

[mikidymac]

An air leak is bad on a 2-stroke, especially a crank seal leak.
Did you grease the inner lips of the seals where the crank rides? You should have.

 

[Jetman454]

I did grease them. Had zero leaks no matter crank position when I installed motor. I'm pulling the motor and changing the seal. Not that I want to, but I know that air leaks kill these motors.

 

[Jetman454]

I think the backfire may have blown it out. All I can figure.

 

[Jetman454]

Well took motor out, cannot find any external leak. Used wd40 and soap and water. Figure it's the inner crank seal. Changed carb springs to the 95gram springs. Pop off at 22 on both carbs. Verified all jets clear and orifices clear. Reinstalled everything. Took to lake runs about 30-40 degrees cooler at idle. Now I have an issue where it dies in the 4500- 5200 rpm range. Not all the time just randomly. Water out of pisser for cylinder head is HOT when coming off high rpm. Feels like it cools of after running at idle. Running the oil pump and 50:1 premix in tank for break in only.

 

[Jetman454]

Gonna pressure check fuel system. All new lines and water separator were installed.

 

[Jetman454]

Well ski runs really good. No hesitation or bogging. However, it still just randomly dies for no apparent reason. It's happened in mid range, low/idle range and wot. Any ideas? Plugs and pistons look ok. Changed fuel filter oring, have new fuel selector on order.