Idle issues

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Rep732 said:
Dammnn... and by the looks of the top of the piston being so clean you had detonation with all those divets in the piston and were very lean. Seeing how that piston looks that top end is trashed
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That sucks. I just have had this one season, bought it used last March. Always ran 25:1 and never leaned it out. My needles were pretty close to stock.
Until this bolt head sheared, the motor always had good compression. The cylinder walls are very smooth. No scoring that I could feel.
My thought was the clean piston head was due to good oil burn. I am using red line racing oil and 92+ octane (some gas stations have 94).
Is this really shot? Will a new gasket not work? New piston and ring maybe?
What does everyone else think?
Seandonato73 said:
Yep agree with phill 100%☝🏻. 4 bolt long block time. You can tear it all apart and lap the cylinder and case to get them mated all nice and flat, but inevitably it will blow another. I'd bet this was the original carb issue. Air leak.
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This happened on my other baja. The Baja from the original post is running fine. New carb is working great.
I should have started a new thread
 
Phill2 said:
Lapping the cylinder and crankcase is a good idea but I'd be looking at the price of getting that done as opposed to a 4 bolt.
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Nah sanding board, file and straight edge is all that's really needed. We'll a sharpie or Prussian blue would help too. But nothing too terrible to finish off the season then think of getting something else.
 
Seandonato73 said:
Nah sanding board, file and straight edge is all that's really needed. We'll a sharpie or Prussian blue would help too. But nothing too terrible to finish off the season then think of getting something else.
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A bit rough but if it works it works.
If I were in the OPs position I'd be buying a Zen 290 if I could afford it.
 
Come now phill, it used to be standard procedure to belt surface heads in automotive and Industrial applications. Biggest down side was the cost of the belts and training people to set the machine up right. Surface finish wad the next "issue but largely negated by proper grit and belt make up. You'd be surprised how flat you can get something with a piece of glass and some sand paper. Let alone a good file and something to indicate low spots. Remember the best machine beds were hand checked for flatness and corrected by hand. We've gotten lazy in the last 10 to 15 years, and made machines to make machines. It's one little cylinder and case. Take about an hour or so to true up. I do agree to be on the look out for a 4 bolt, but no reason to toss something thats easily fixed.
 
Seandonato73 said:
Come now phill, it used to be standard procedure to belt surface heads in automotive and Industrial applications. Biggest down side was the cost of the belts and training people to set the machine up right. Surface finish wad the next "issue but largely negated by proper grit and belt make up. You'd be surprised how flat you can get something with a piece of glass and some sand paper. Let alone a good file and something to indicate low spots. Remember the best machine beds were hand checked for flatness and corrected by hand. We've gotten lazy in the last 10 to 15 years, and made machines to make machines. It's one little cylinder and case. Take about an hour or so to true up. I do agree to be on the look out for a 4 bolt, but no reason to toss something thats easily fixed.
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Very true Sean but why waste the time on it?
We used to use Blue as an indicator but I wouldn't even know where to find it these days.
 
Phill2 said:
Very true Sean but why waste the time on it?
We used to use Blue as an indicator but I wouldn't even know where to find it these days.
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Amazon, eBay not hard to get dykem makes it.
Idk I look at it this way, he'll have all of $40.00 or so into fixing it to get going again. $200.00 ish for a long block, finish out the sumer with it and replace the turd over the off season. He gets a little more familiar with his rigs engine and is really non worse off. Now if the cylinder was trash then yeah I can see just replacing it.
 
Seandonato73 said:
Amazon, eBay not hard to get dykem makes it.
Idk I look at it this way, he'll have all of $40.00 or so into fixing it to get going again. $200.00 ish for a long block, finish out the sumer with it and replace the turd over the off season. He gets a little more familiar with his rigs engine and is really non worse off. Now if the cylinder was trash then yeah I can see just replacing it.
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Thanks for all the guidance folks!
Really appreciate it.

I think I will start with the cheapest solution first... My take is, this motor has lasted several years with 2 bolts, a new piston and ring and gasket have to last one or two more... very cost effective (about $30)
I knew coming into this with a used rig eventually I would need to replace the motor, but didnt count on COVID impacting my paycheck (lost job, back to entry level job)... I have some side gigs and will save up some of that for a Zen.

So a few last questions:
1) is the .020" copper gasket the right one?
2) should I buy the squish indicator tool too?
3) what is the bolt size for the head?
4) If I get the 29cc Zenoah long block, will my cy26 bits finish it off? is it compatible? (flywheel, clutch housing, etc)
 
No no 5mm.
Squish needs checked before you go and buy anything. All you need is some solder and a calipers to measure the solder.
Place the solder inline with the wrist pin (use a bit of grease to hold it. Lead solder works best for this) bolt the head on with out the gasket. Turn the engine over and squish the solder to get the clearance. Pop the head off and measure what you got. Get the gasket that gets you closest to .020" of your way over .020" to begin with then get the thinnest gasket and use that. I think it's. 005".
 
Seandonato73 said:
No no 5mm.
Squish needs checked before you go and buy anything. All you need is some solder and a calipers to measure the solder.
Place the solder inline with the wrist pin (use a bit of grease to hold it. Lead solder works best for this) bolt the head on with out the gasket. Turn the engine over and squish the solder to get the clearance. Pop the head off and measure what you got. Get the gasket that gets you closest to .020" of your way over .020" to begin with then get the thinnest gasket and use that. I think it's. 005".
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I don't have calipers or know anyone who does...
Actually Amazon has a caliper for $18... next day delivery too...
 
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Seandonato73 said:
No no 5mm.
Squish needs checked before you go and buy anything. All you need is some solder and a calipers to measure the solder.
Place the solder inline with the wrist pin (use a bit of grease to hold it. Lead solder works best for this) bolt the head on with out the gasket. Turn the engine over and squish the solder to get the clearance. Pop the head off and measure what you got. Get the gasket that gets you closest to .020" of your way over .020" to begin with then get the thinnest gasket and use that. I think it's. 005".
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I am sorry, the last part is not clear to me....

I got some calipers, and I noticed my solder is not squished evenly. which Part of the solder am I measuring?
Closest to the cylinder wall is .0275, and closest to the piston center is .0150
I measured again on both sides of the cylinder... at the thinnest part of the solder, closest to the center I go down to .0135

So a .005 copper gasket gets me to .0185
Do I want to be over .02 or under .02? or are we aiming for as close as we can get?
The next sized gasket is .012 --> so we would be at .0255
 
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