engine lock up

[Dale Sonnenschein]

Hey all,
This is a short story made long, so heres my story,
I bought my jackpiner last fall. It needed a lower rod bearing along with a clean up. I rode it for the first time about a month or so ago. It felt weak so it was bored and a new piston. I broke it in easy but never got past 2nd gear. At unadilla on the CC parade lap something got tight and stalled the engine. It started up fine. Rode it a little further and it did it again. I could hear the engine labor and then stall again. It did it once more before I got it back to the pits. I thought maybe the bore was tight and that caused it. I rode it some at home and it was fine till about 10 minutes into the ride and it did it again. I was going along in 3rd gear, it locked the rear wheel and before it stopped I pulled the clutch in and it rolled to a stop. I pulled the head and the cylinder looks fine. No scores or sign of heat.I mixed the oil about 35:1 for break in. Since it's not the top end, what could it be? My thought is something in the clutch since it rolled ok with the clutch in. Any idea's?

73 Jackpiner
73 Husky 360 WR/RT
76 Husky WR360
78 husky cr250
10 ktm 250xc
02 bmw r1150r

[454MRW]

Without knowing what clearance the borer allowed for your piston, I would start by checking that. New bikes are set up a lot tighter, so make sure your machinist followed the piston recommendations, usually around .0035". Also that oil hole(s) are drilled in the exhaust side of the piston for oiling/cooling if you have a bridged exhaust port. Examine the piston through the port with the pipe off for signs of rubbing or seizure. Mike

Michael R. Winter
I enjoy rebuilding and appreciating Pentons!
1974 250 HS Pentons-1978 KTM 250'S
1975 Can Am 175 TNT 250 conversion
1976-78 125-400 RM's & 79 PE250 Suzuki & 2012 DR650
2007 CR125R Honda
1977 MC250 Maico

[Dale Sonnenschein]

The directions that came with the piston were .0020-.0025. I'll check the piston but the cylinder looks good. Yes, the oil holes were drilled. The bike kicked over and started 5 to 10 seconds after it stalled and ran 3 or 4 minutes and did it again. The last time it did it I rode for at least 10 minutes.

73 Jackpiner
73 Husky 360 WR/RT
76 Husky WR360
78 husky cr250
10 ktm 250xc
02 bmw r1150r

[Daniel P. McEntee]

Since you had to split the cases to do a lower rod bearing, I would investigate there. either the rod is tight on the crank, or something in the crank bearings. Drain your tranny fluid and see what it looks like. Check crank for pend play, and see if the rod feels funny. I'm guessing bottom end issue.  Since the bore looks that good after the sudden stopping, I wouldn't think any kind of seizing is going on.
   Good luck with it,
  Dan McEntee

[Dale Sonnenschein]

Ok, Just pulled the cylinder. The piston has a rub mark on the intake side dead center from the intake bridge. The exhaust side has a rub mark on the left side of the exhaust port. You can't catch a finger nail on them but they are "polished" for lack of a better word. I'll take the cylinder to the machinist for his opinion. The rings are free and the polished parts are below the rings.

73 Jackpiner
73 Husky 360 WR/RT
76 Husky WR360
78 husky cr250
10 ktm 250xc
02 bmw r1150r

[slvrbrdfxr]

Dale
What did you set the deck height to ?? I had a similar issue with a bike several years ago in which I had set the deck height at the minimum to get the max compression from a freshly bored cylinder. Once I reset the deck height to closer to the maximum limit the trouble disappeared and bike ran great.
Dave McC

[Dale Sonnenschein]

Dave, I set the deck at the spec in the manual. I have 2 base gaskets on it. I don't remember the number. I think the previous owner had a new piston put in and he gave me a letter from penton that says to use one step colder plug with a bored cylinder. I didn't read the letter till now. Also it says what clearance to use with each bore size. For competition is shows .003 to .0035. Mine was set at .002 to .0025.

73 Jackpiner
73 Husky 360 WR/RT
76 Husky WR360
78 husky cr250
10 ktm 250xc
02 bmw r1150r

[454MRW]

Depending on your jetting it could be getting a little tight once fully warmed up. A little extra clearance, especially ring end gap, is better than too little. Mike

Michael R. Winter
I enjoy rebuilding and appreciating Pentons!
1974 250 HS Pentons-1978 KTM 250'S
1975 Can Am 175 TNT 250 conversion
1976-78 125-400 RM's & 79 PE250 Suzuki & 2012 DR650
2007 CR125R Honda
1977 MC250 Maico

[Dom Sileo]

What he said ^^^^^

[Dale Sonnenschein]

Jetting is a 35 pilot and a 150 main. The premix is 35-1. I thought a little more oil won't hurt. I'm taking the piston and cylinder to the machinist tonight. The previous owner had a piston put in and he gave me a letter from penton saying to run one step colder plug. What's your thoughts? That was the recommendation with a penton piston. I put in a wiseco piston.

73 Jackpiner
73 Husky 360 WR/RT
76 Husky WR360
78 husky cr250
10 ktm 250xc
02 bmw r1150r

[SouthRider]

Keep in mind that the more oil you add the leaner your mixture is.
It's generally not a good idea to add more oil than recommended.

Better to run the same premix at all times & jet accordingly.

_____________________________________________________________________________________

"We the willing, led by the unknowing, are doing the impossible, for the ungrateful. We have done so much, for so long, with so little, that we are now qualified to do almost anything, with nothing."

1972 Penton Berkshire 100
1983 Husqvarna 250 XC
2011 Jayco 31.5 RLDS
2009 Chevy 2500 HD Duramax

[454MRW]

The difference from 32:1 and 35:1 or even 50:1 is almost non-existent in the amount of fuel amount changed. What matters is what the spark plug looked like after fully warmed up and a full throttle run with a coast in neutral engine off shut down, however with the situation at hand of getting tight, it would not be possible or recommended. In this case I would jet it a little richer once you get the piston/bore re-sized and check the ring end gap in the re-adjusted cylinder bore! Every engine is different in actual jetting requirements, and engine timing also plays a huge factor in engine heat, so you might double check the timing as well. Personally I run Golden Spectro at 32:1 and 93 Octane Marathon pump gas in all my bikes with no issues. Mike
Here is a POG response to clearances for a Jackpiner from back in 2004.

Max allowable piston to cylinder clearance:
175cc -- .006" to .007"
Specs for ring end gaps:
175cc -- .010" to .012" minimum
.018" to .020" maximum
Clearance specs for boring cylinders:
175cc -- .003" to .0035

Michael R. Winter
I enjoy rebuilding and appreciating Pentons!
1974 250 HS Pentons-1978 KTM 250'S
1975 Can Am 175 TNT 250 conversion
1976-78 125-400 RM's & 79 PE250 Suzuki & 2012 DR650
2007 CR125R Honda
1977 MC250 Maico

[Dale Sonnenschein]

Mike, You are right that I couldn't run a jet test. I'm sure it wouldn't have made the wide open run. The bore spec from wiseco was .002 to .0025. It was at .002 and it must have been too tight. The machinist honed the cylinder to .003. When it seized it didn't hurt the piston. So I am going to change the rings and give it a go. I usually run 40:1 in my modern bike so that's what I will run in this.

73 Jackpiner
73 Husky 360 WR/RT
76 Husky WR360
78 husky cr250
10 ktm 250xc
02 bmw r1150r

[454MRW]

Square each ring in the cylinder with the loose piston before installing them on the piston and check the end gap with a feeler guage on each ring and file as needed to obtain the minimum gap. This is critical. Mike

Michael R. Winter
I enjoy rebuilding and appreciating Pentons!
1974 250 HS Pentons-1978 KTM 250'S
1975 Can Am 175 TNT 250 conversion
1976-78 125-400 RM's & 79 PE250 Suzuki & 2012 DR650
2007 CR125R Honda
1977 MC250 Maico

[Dale Sonnenschein]

Rings gapped and back together. Just took a quick 10 minute run and it seems to be running good. It bogs a little and starts to load up in low rpm's. I'll try some minor carb adjustments to get it running top notch.

73 Jackpiner
73 Husky 360 WR/RT
76 Husky WR360
78 husky cr250
10 ktm 250xc
02 bmw r1150r