I have a 150 cylinder and have bought a replacement cylinder head due to the original being damaged. (all came as part of a full engine off ebay)
It wasn't until I got the replacement that I measured the cylinder and head and the original is 62mm across, the replacement is 62mm.
Can I use the replacement head?
Am I right in saying the original has been rebored to 175? Is it worth my while getting it rebored any further or am I better off getting a new kit?
Is there anyone in the Brighouse area who can do a rebore?
Cheers
Nick
Rebore info needed
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bristolmod
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- Main scooter: Lambretta TV175 S3- what else!
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its either:-
1) a 150 top end thats been rebored to 62mm (175cc) with the head reprofiled to match (check on head - does it say 150 or 175)
2) a standard 175 cylinder with a reprofiled head or a 175 head. This would have used a conversion 175 piston if it was running the original "LI" type crank
3)a "proper" 175 cylinder, head and crank
Obviously a "proper" 175 cylinder will rebore better than a "150" (and have much bigger ports), but the 150 to 175 conversion is a common one.
Chris
1) a 150 top end thats been rebored to 62mm (175cc) with the head reprofiled to match (check on head - does it say 150 or 175)
2) a standard 175 cylinder with a reprofiled head or a 175 head. This would have used a conversion 175 piston if it was running the original "LI" type crank
3)a "proper" 175 cylinder, head and crank
Obviously a "proper" 175 cylinder will rebore better than a "150" (and have much bigger ports), but the 150 to 175 conversion is a common one.
Chris
Scootering since 1968.
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nickw1969
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Hi Chris,
The original head is a 150, which looks like it has been reprofiled. I have got a new GP crank in the engine already and want to keep costs down if possible.
Can I use the new standard 150 head, or should I get a new 175 head?
I am considering a new kit anyway, but if I can get a 175 head on the cheap I may as well give it a go and only swap it out if necessary.
There is a bit of "blow back" on the piston, - will a new set of rings help with this, or is it a sign of something more serious? The piston fits nicely in the cylinder, within the range specified in stickys manual.
Cheers
Nick
The original head is a 150, which looks like it has been reprofiled. I have got a new GP crank in the engine already and want to keep costs down if possible.
Can I use the new standard 150 head, or should I get a new 175 head?
I am considering a new kit anyway, but if I can get a 175 head on the cheap I may as well give it a go and only swap it out if necessary.
There is a bit of "blow back" on the piston, - will a new set of rings help with this, or is it a sign of something more serious? The piston fits nicely in the cylinder, within the range specified in stickys manual.
Cheers
Nick
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joespeed
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- Location: drax,near selby,north yorkshire
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could try this man richard redline racing 01484 717792nickw1969 wrote:I have a 150 cylinder and have bought a replacement cylinder head due to the original being damaged. (all came as part of a full engine off ebay)
It wasn't until I got the replacement that I measured the cylinder and head and the original is 62mm across, the replacement is 62mm.
Can I use the replacement head?
Am I right in saying the original has been rebored to 175? Is it worth my while getting it rebored any further or am I better off getting a new kit?
Is there anyone in the Brighouse area who can do a rebore?
Cheers
Nick
-
bristolmod
- registered user
- Posts: 1741
- Joined: Wed Jan 07, 2009 8:42 am
- Main scooter: Lambretta TV175 S3- what else!
- Location: Bali-Hai bar, Locarno Ballroom Bristol, 1967!- mines a Brown Split!!
- Contact:
What you could try first:-
1) use existing reprofiled head
2) new set of rings (is there a size on the existing piston?)
3) "glazebust" the barrel, otherwise the new rings won't bed in. You can do this yourself with some wet and dry.
Alternatively, get hold of the next size piston (make sure its the same gudgeon pin height as the old one)
Give the new piston (without rings, pin etc) and barrel to your local friendly reborers and ask him to rebore to fit (I specify 3 1/2 thou clearance on iron barrels)
The bloke I use in Bristol is really good- I think I paid £20 recently for a rebore and hone. He probably does mail order but you need to factor in the postage costs which won't be cheap.
TBH most pistons can show some evidence of "blowback"- depends on how much is involved. What is the compression like?
Whatever you do, do NOT use a standard 150 head (58mm) on a 175 barrel (62mm)- a reprofiled one (out to 62mm) is fine as long as its reprofiled correctly.
Chris
1) use existing reprofiled head
2) new set of rings (is there a size on the existing piston?)
3) "glazebust" the barrel, otherwise the new rings won't bed in. You can do this yourself with some wet and dry.
Alternatively, get hold of the next size piston (make sure its the same gudgeon pin height as the old one)
Give the new piston (without rings, pin etc) and barrel to your local friendly reborers and ask him to rebore to fit (I specify 3 1/2 thou clearance on iron barrels)
The bloke I use in Bristol is really good- I think I paid £20 recently for a rebore and hone. He probably does mail order but you need to factor in the postage costs which won't be cheap.
TBH most pistons can show some evidence of "blowback"- depends on how much is involved. What is the compression like?
Whatever you do, do NOT use a standard 150 head (58mm) on a 175 barrel (62mm)- a reprofiled one (out to 62mm) is fine as long as its reprofiled correctly.
Chris
Scootering since 1968.
