Post by dando127 on Nov 12, 2021 6:57:32 GMT
GaWajn
A buddy brought me a 1971 TNT 340 ... or what he thought was one ...
The crank case halves are numbered 912-080 and 912-090 and should be the same as a 335 if I am not mistaken. The crank stub is a 7\8th.
A rough measurement of the cylinder gave me 77.98mm. There is a rounded aspect to the top of the piston ... more so than a 335.
The cylinder and head have no numbers on them. The carb that came with it is an HD-22B.
Does the clutch look right?
Is this a 1971 340? The shroud says 78mm - 70mm - 335.
skidog59
that's a replacement clutch but everything looks in check. that's a 340 tnt motor. they shared a lower end with the 71 and up olys
GaWajn
Thanks for the quick response. Should the shroud say 342 instead of 335?
Bones
I totally agree with skidog59, and add....the crank case for a `71-73 - 335/337 Oly engine, `71 - 340 TnT engine and the 71/72 - 292 engines were all the same, just the 292 had a shorter stroke crank.
Yes the 71 - 340 tnT piston will have a taller crown than a Oly piston. The `71 - 340 TnT pistons are getting extremely hard to find. You can use a Oly piston but with the 71 - 340 head you will be down a bit on compression.
There is no doubt the piston you have pictured is a TnT piston
Bones
GaWajn
Thanks a bunch guys. I am working on a340 single that has a wrong shroud (reads 335) and an incorrect clutch ... right? everything else checks out? Any ideas to what year/engine that clutch belongs? I am going to use that clutch ... but I am assuming that the orange part should be black for a 1971?
Another question ... since the bore is the same ... if I want to put new rings to the TNT piston ... regular 335 type rings will work ... correct?
Bones
I doo not believe the shroud ever said 342, I believe if it says 335 it is correct.
The orange governor cup started in `72 I think, most likely work OK.
NO, you CAN NOT use Olympic piston rings The rings are what confirmed a TnT piston to me If you have a Oly piston/rings on hand....compare the ends of the rings, you will see the difference
Bones
Bones
Governor cup # 582-1028 was used: 73 Elan 250E, 73 Olympic 300 & 335, 73 Olympic 340 & 400 twin & skandic 335.
Bones
GaWajn
I see what you mean by the ring shape Bones. Thank you very much for the info guys.
skidoo292
I am glad you posted this GaWajn,
I brought home a 71 340 TNT also that I found the same info on the engine tag. I had been wondering if someone had put a 335 shroud on it.
I knew the rest of the engine was right because of the hd carb etc.
So now I know that is the way the tags were ...thanks
GaWajn
It's all good
The guy I am rebuilding this engine for ... is wanting to put a stinger pipe on it. I have sent a message of to Goose about this. Is there anything special I should be aware of with using a stinger pipe with this sled?
skidog59
I have an original pipe that was either a dougs or straight from ski doo. every sled we have put it on (2 or 3 340's and a 292) have burned a hole in the piston. I'm thinking the timing may need to be retarded while running my particular pipe. Not sure about gooses pipes.
GaWajn
Thanks for the info about burning pistons. Does anyone have a spec for the timing that should be used with a stinger?
Now that I see how to ID a 340 ... what are the traits to look for when trying to ID a 292? Or is there a thread where this was all hashed out?
70Oly399
292 will look pretty much like a 335 except for an HD carb not the HR and it won't have a decompressor.
GaWajn
Will it say 292 on the fan shroud?
Also ... as an aside question on engine ID ... I just got a cast ironed cylinder 250 with the rounded head ... which could mean from 1963 to 1968 ... but if I am not mistaken ... 1968 was the first and only year of the decompressor near the exhaust port, on a cast iron cylinder, 250 engine ... correct?
A buddy brought me a 1971 TNT 340 ... or what he thought was one ...
The crank case halves are numbered 912-080 and 912-090 and should be the same as a 335 if I am not mistaken. The crank stub is a 7\8th.
A rough measurement of the cylinder gave me 77.98mm. There is a rounded aspect to the top of the piston ... more so than a 335.
The cylinder and head have no numbers on them. The carb that came with it is an HD-22B.
Does the clutch look right?
Is this a 1971 340? The shroud says 78mm - 70mm - 335.
skidog59
that's a replacement clutch but everything looks in check. that's a 340 tnt motor. they shared a lower end with the 71 and up olys
GaWajn
Thanks for the quick response. Should the shroud say 342 instead of 335?
Bones
I totally agree with skidog59, and add....the crank case for a `71-73 - 335/337 Oly engine, `71 - 340 TnT engine and the 71/72 - 292 engines were all the same, just the 292 had a shorter stroke crank.
Yes the 71 - 340 tnT piston will have a taller crown than a Oly piston. The `71 - 340 TnT pistons are getting extremely hard to find. You can use a Oly piston but with the 71 - 340 head you will be down a bit on compression.
There is no doubt the piston you have pictured is a TnT piston
Bones
GaWajn
Thanks a bunch guys. I am working on a340 single that has a wrong shroud (reads 335) and an incorrect clutch ... right? everything else checks out? Any ideas to what year/engine that clutch belongs? I am going to use that clutch ... but I am assuming that the orange part should be black for a 1971?
Another question ... since the bore is the same ... if I want to put new rings to the TNT piston ... regular 335 type rings will work ... correct?
Bones
I doo not believe the shroud ever said 342, I believe if it says 335 it is correct.
The orange governor cup started in `72 I think, most likely work OK.
NO, you CAN NOT use Olympic piston rings The rings are what confirmed a TnT piston to me If you have a Oly piston/rings on hand....compare the ends of the rings, you will see the difference
Bones
Bones
Governor cup # 582-1028 was used: 73 Elan 250E, 73 Olympic 300 & 335, 73 Olympic 340 & 400 twin & skandic 335.
Bones
GaWajn
I see what you mean by the ring shape Bones. Thank you very much for the info guys.
skidoo292
I am glad you posted this GaWajn,
I brought home a 71 340 TNT also that I found the same info on the engine tag. I had been wondering if someone had put a 335 shroud on it.
I knew the rest of the engine was right because of the hd carb etc.
So now I know that is the way the tags were ...thanks
GaWajn
It's all good
The guy I am rebuilding this engine for ... is wanting to put a stinger pipe on it. I have sent a message of to Goose about this. Is there anything special I should be aware of with using a stinger pipe with this sled?
skidog59
I have an original pipe that was either a dougs or straight from ski doo. every sled we have put it on (2 or 3 340's and a 292) have burned a hole in the piston. I'm thinking the timing may need to be retarded while running my particular pipe. Not sure about gooses pipes.
GaWajn
Thanks for the info about burning pistons. Does anyone have a spec for the timing that should be used with a stinger?
Now that I see how to ID a 340 ... what are the traits to look for when trying to ID a 292? Or is there a thread where this was all hashed out?
70Oly399
292 will look pretty much like a 335 except for an HD carb not the HR and it won't have a decompressor.
GaWajn
Will it say 292 on the fan shroud?
Also ... as an aside question on engine ID ... I just got a cast ironed cylinder 250 with the rounded head ... which could mean from 1963 to 1968 ... but if I am not mistaken ... 1968 was the first and only year of the decompressor near the exhaust port, on a cast iron cylinder, 250 engine ... correct?
