98 xp limited Leaking exhaust in engine bay

[dthomas00]

It has a new sbt motor, I used the brake in procedure and it ran good for about an hour.
Then it started getting hot and made a high pitched noise and would not go past 5000 rpm's and smoke pours out of the engine bay when it is opened. I changed the plugs becouse they had become fouled out but it didn't help.
I also have another 98xp limited that ran good for about an hour and now will not start, it sounds like it backfires when you try to start it. The engines were put in at the same time. I bought the pair with the new enines already installed so I don't know who put them in.
Any help would be appericiated.
thanks

[ccwhit7]

Did both have oil in the gas ?

[stevepaulus]

Timing could be off...i did the same thing when i put my 97 Xp back together. I didn't line up the magneto cup with the tiny hole on the flywheel...and it backfired like a bi@@, scared the hell out of me and blew a hole the size of my fist in the exhaust hose.

Just a suggestion to start looking at.

[dthomas00]

yea there was oil mixed in the gas for break in

[Technical Support]

For the one that started backfiring, pull the carbs off and check the reeds for broken petals.

For the other, idle it on the hose and locate the source of your exhaust leak - you will see smoke, it could be as simple as a melted rubber coupling on the exhaust from getting hot, you might have a cooling line issue.