Ultra 150 Crankcase

[Jimbob]

Hi,

I've liened out & seized the #1 cylinder twice in one week. Replacing cylinders & pistons is getting old & expensive. I've taken apart and cleaned the carburetor and found nothing worn, torn, or plugged. Oil flow is fine. Can low crankcase compression cause a lien condition resulting in siezure? Anything else I should check? Thanks ..... Jimbob

[Bryan Glynn]

Did you pressure check the engine?

No, low compression cannot cause a lean condition.

[Jimbob]

Hi,
Cylinder compression is about 120psi on #2 and #3; consistently. Compression on #1 cylinder is toast after the seizure. (Its definitely gone lien .... **** near burned a hole thru the piston & plug looks like a charcoal briquette!) I have no way to pressure test the crankcase .... I guess I would need block-off plates for the intakes; I'm just not set up for that kind of work. I thought that after the seizures, enough junk might have gotten into #1 crankcase and damaged the seals, causing low crankcase compression. Jimbob

[Bryan Glynn]

If you're not setup for that then you should be trying to build an engine, no offense.

You could also have a bad fuel obstruction issue, possibly at the switch, or intake, etc.

[Jimbob]

Hi,

None taken. I'm pretty new to the 2-stroke world and am still learning. I learn by trial & error; its expensive, but I only make each mistake once! Chevy small-blocks are more my speed!

If I knew-for-sure the problem was the crankcase, I'd order a new block. But, it looks like I'd just toast it because the problem is probably in the fuel system somewhere!
If I bring it to a dealer, it could take up to a month before I get it back.

Thanks for your time and effort. Jimbob

[Bryan Glynn]

Oh I agree - slapping in a new shortblock could be your fastest way to wasting $1500.

Definitely take the time and spend the mmoney to get everything checked out and find the cause first.

[skiworx]

Hi, have you checked to make sure theres no clog in the cooling? Ultra's have issues with over heating and cooking cylds. is the flow from the front pisser flowing good? The front and rear cylds get 50% if there oil from the cases and 50% from the pump so you have to make sure the oil flow to the front case is good also, not just the flow to the carb..

[Jimbob]

Hey,

Water flow is wonderful; but I'm gonna be checking the oil flow. We all check to be sure the cylinders are getting their share of the oil, but the front & rear bearings are another story. I'm pretty sure I found the problem to be the front seal; I did a crankcase compression check and the front seal was leaking like a sieve. jhr

[Jimbob]

I forgot,

Does anyone have any experience with the starter clutch? When I reassembled the crankcase and torqued the flywheel/magneto bolt to the specified 90 ft/lbs, the gear siezes; (it seems okay at 50 ft/lbs, but more torque tightens it up till there's no clutch action) I've checked all the parts and everything looks good. I'm wondering if there's a problem with the 90 ft/lbs specified in the manual. Thanks ...

[raider1100]

If the crank seal for the #1 cylinder is installed improperly or is leaking than that could cause a lean condition
Rob

[skiworx]

Jimbob, I have had that problem before with the starter clutch before..There are 2 tapered spacers on each side of the sprag, they are different sizes so be sure you have them in correct and be sure you have the taper the correct way also if my mind is working right I believe I have a time or two left the smaller spacer out so that it would spin freely...

[Jimbob]

Hey Ho,
The main problem was the front seal. I replaced it but the flywheel bolt now baffles me. I am aware of the two washers which are tapered, but still no worky. Its very frustrating when solving one problem leads to another. Thanks for the help ..... keep 'em coming. jhr