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March 25, 2019, 09:47:01 AM
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 1   oldski-doosleds Message Board / One-Lunger Help Desk (Only) / Re:340 Single Oversize  on: Today at 04:37:04am 
Started by jerryswiss | Last post by jerryswiss
Thanks Bones, it is definitely a 1971 machine, as by the serial number, so with that aftermarket piston in it, that would explain why the compression is low. I think I will try a copper head gasket and see what happens.

I am actually able to get some pretty good gas around here, 91 octane no ethanol. That is all I put in all small engines.
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 2   oldski-doosleds Message Board / One-Lunger Help Desk (Only) / Re:340 Single Oversize  on: March 24, 2019, 08:51:29 PM 
Started by jerryswiss | Last post by Bones
You ask " is there any piston and ring set I can fit in this engine" Yep, ones like you have are out there by the 1000s 
Your engine is NOT bored 80 over, it is in fact standard 
If you bore a 340 single cylinder to 80 over there is nothing left of the sleeve, you can`t doo it. 40 over really is max you should go. There is no question you have a aftermarket piston in there. Here is some FYI for you...….The piston for a 71 to 78 Rotax  type 302 (299cc) and the 69 - 320 cc are actually 100% the same piston and are standard of 76 mm. The piston for a 70 to 73 - 335 Olympic engine is also 100% identical in shape to the 300/320 piston but it is 78 mm as standard. so many, many of the aftermarket companies used the same tooling and made a standard piston of 76 mm then carried on with 76.5 at 20 over, 77 mm as 40 over, 77.5 mm as 60 over, 78 mm as 80 over, 78.5 as 100 over and ending at 79 mm as 120 over.  The piston marked as 80 is actually 78 mm and is std for the 345/340. You would use the 120 over as actually 40 over for the 340.
Have you figured out if you have a 70 or 71 head They are different. ALL aftermarket pistons are made to match the 70 head and are too low on the dome for a 71 head, compression is DOWN with the piston like you have and a 71 head. The correct piston to match the 71 head are near impossible to find. Aftermarket companies NEVER made a piston to match the 71 - 340 TnT head.
I set up a engine a few years ago with the low dome piston and a 71 head so the compression/squish was intentionally low to run the garbage fuel we have today. I doo not recall what the compression was but I am sure it was above 108 as you are getting. The engine will still run fine, if you are not racing, it is fine for a trail sled IMO.
I thin copper head gasket might work OK, I don`t really have a opinion on that.
Bones
Bones
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 3   oldski-doosleds Message Board / One-Lunger Help Desk (Only) / 340 Single Oversize  on: March 24, 2019, 07:23:42 PM 
Started by jerryswiss | Last post by jerryswiss
Ok, I am working on a '71 340 TNT single and I start scraping the carbon off the top of the piston and what doo I see? 080! So this cylinder has been WAY over sized. First question is WHY? The odometer only shows 950 miles, and I know the cable could be bad, but when I look at the track, it looks like new.

Second question, this motor does not have that great of compression (108 psi at 4800 ft). So is there any piston and ring set I can still fit in this engine? The piston and cylinder actually do not look that bad, no cylinder rim or gouges.

I was thinking of just putting a copper head gasket on it and seeing what happens. Thoughts?
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 4   oldski-doosleds Message Board / Vintage ski-doo General Disscusion / Re:Large day  on: March 24, 2019, 07:02:21 PM 
Started by Rockalicious | Last post by EricR
Yep, I was sore after this day back in December!

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 5   oldski-doosleds Message Board / Vintage ski-doo General Disscusion / Re:Large day  on: March 24, 2019, 12:37:05 PM 
Started by Rockalicious | Last post by Rockalicious
oh jeez... rough on the machines and the body, but good stories for them later on when they are older!

Speaking of the body, I can feel my back and legs this morning. I can barely bend over! Riding like that once a year makes you forget how much you use those muscles. Probably doesn't help that I am 200lb and 6'3", a bit too big for the might elan.
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 6   oldski-doosleds Message Board / Vintage ski-doo General Disscusion / Re:Large day  on: March 24, 2019, 12:10:54 PM 
Started by Rockalicious | Last post by Elan Dude

Quote from: EricR on March 24, 2019, 07:27:11 AM   

It doesn't help that three years ago I put my then 9 year old on the Elan and told him "This is the gas and this is the brake" not thinking that he would just pin it to the bar and panic. He plowed right in to a trampoline 40 feet away, smashed his face in and two black eyes/emergency room visit. Totally my fault. Now he's scared of it.


Love the photos Rock

Great story Eric. In my case, I forgot to tell my 5 year old grandson how to use the brake. You could see him in front of me on the attached picture. On that day he wanted to follow for whatever reason. Mistake! After riding for 10 minutes I decided to check how he was doing. I stop, turned around and before I knew it he rear ended my Everest. The Everest hitch punctured a pretty nice hole in the Elan hood. Very calmly he said, grand papa you never told me how to stop. He is 10 now and he graduated to the Everest after riding his dad 76 Olympic for 2 years.

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 7   oldski-doosleds Message Board / Vintage ski-doo General Disscusion / Re:Large day  on: March 24, 2019, 09:33:19 AM 
Started by Rockalicious | Last post by Joe Olympique
Love that white elan of yours.  I had a project sled like that one, since sold.  I could never decide if I would dress it up as Penguin or raccoon.
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 8   oldski-doosleds Message Board / Vintage ski-doo General Disscusion / Re:Large day  on: March 24, 2019, 07:27:11 AM 
Started by Rockalicious | Last post by EricR
It doesn't help that three years ago I put my then 9 year old on the Elan and told him "This is the gas and this is the brake" not thinking that he would just pin it to the bar and panic. He plowed right in to a trampoline 40 feet away, smashed his face in and two black eyes/emergency room visit. Totally my fault. Now he's scared of it.
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 9   oldski-doosleds Message Board / Vintage ski-doo General Disscusion / Re:Large day  on: March 24, 2019, 06:49:07 AM 
Started by Rockalicious | Last post by Rockalicious

Quote from: EricR on March 23, 2019, 03:52:21 PM   

Looks like a beautiful day! Yeah, once upon a time my kids would come scramblin' out the door to ride on anything dad was on even if it was in my lap mowing the lawn, but now I got to pry them out!


It's unpredictable for my 8 and 10 year old. They have so many distractions compared to what I had when I was their age. I planted the outdoors/ski doo seed (hopefully), just trying to keep it alive the best I can from here on in.
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 10   oldski-doosleds Message Board / Help Desk (Only) / Re:15 x 114 wide window track  on: March 23, 2019, 06:14:05 PM 
Started by rick | Last post by Bones
I agree, the wide window 114" tracks work perfectly well with the narrow sprockets. I believe the OEM tracks are a slight bit narrower from outside to outside of windows compared to the Dayco. So the OEM stays centered slightly better, but no problem to use the Dayco.
Bones
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