No head gasket with hi comp piston recommended.

[epod]

G'day. Just picked up a 55.5mm "High speed" high comp piston from Akuna and was advise that running a head gasket is not necessary and even inhibits performance. What do you think fella's. Has anybody needed to shave this piston for valve clearance in the Lifan 138 alloy barrel, oil cooled from case's . (really 127 I know, but not for long.) Just gotta get my barrel bored out.
Peace, Ride on.

 

[CHINGArider]

Hey mate I recently fitted on of these pistons to the same engine with the gasket it came with. It now has a nasty tapping sound which is hard to tell where its coming from. Ive removed the head again and cant see any damage from valve/piston/head contact. Im struggling to work this out, if anyone has any info about installing these pistons and what this could be id greatly appreciate it as would epod.

 

[epod]

Weird

G'day mate. Don't know about that, except that piston might be hittinga valve. I was told slight shaving of the piston might be necesary for proper valve clearence.
Good luck, let me know how you go.

 

[Hillz]

you should alway run a head gsk it's just stupid not to run one! but they proberly said that coz the carn't get you the right size head gsk.

Yes this will be the noise you are hearing, the piston hitting the head gasket coz the hole is not big enough.

the best way is to make/get made a copper head gsk

 

[andy600rr]

You will most likely need to enlarge the valve relief's in the piston slightly (I had to on mine).

Also as Hillz said, make sure you use a correct size head gasket or your piston WILL hit the gasket and cause all sort of fun things to happen.

Give Big50 a call and they can help you out with an alloy 56mm head gasket and drop into your local auto parts supplier and buy a can of VHT coppet gasket spray to go with it.

http://www.big50raceandretroparts.com.au/index.php

 

[epod]

Thanks, what are the valve reliefs

Are are the valve reliefs, how do I enlarge them. Can I just get the machinist to do it when he does the rebore? Far out 2 strokes are so much simplier, these 4strokes blow my mind sometimes. Thanks for all the help fella's.
Ride on.

 

[Hillz]

yeah the bore dude should be able the relieve the valve pockets for you,
however wit ha metal head gasket which will be anywhere from .5mm to 2mm they may not need it

 

[epod]

Has anybody bored 138/127 barrel from 54 to 55.5

Thanks again fella's. I called retro 50's they told me it is very risky trying to bore these alloy lifan barrel's any further. They are 54mm x 57mm stroke, 14mm piston pin. I want to bore out to fit a 55.5mm piston. Retro 50's did not have a gasket for me, would only sell me a complete kit with 56mm barrel japanese piston, $320. Also has anybody resleved one of these a cycliners.
Ride on.

 

[CHINGArider]

If the bore is done properly there is still plenty of meat left on the sleeve. Check out how thin rkfinch has gone with his and has no problems.
http://www.miniriders.com.au/forum/attachment.php?attachmentid=358&d=1166675172
Mine still had heaps more left on it. Id say theyre just trying to make a few more bucks out of ya.

 

[epod]

Sorry for spudid question Chingarider, you have bored yours same motor as mine.

Hey Chingarider, glad to here you had not problem boring the barell. Have you fixed the noise problem yet? Was it the gasket being to small. How much to bore your barrel? Please let me know when you get it sorted because I am wondering how much exrta torque the bike has. All the best mate.
Rise on.

 

[epod]

Thanks again.

You already answered that one to.

 

[CHINGArider]

Yeh mate I havent got around to refitting the head yet but after closer inspection im suspecting the inlet valve might be slightly fouling on piston. Ill try enlarging the valve relief tomorrow and let u know how it goes.

 

[epod]

How do you do that?

Cheers. How will you enlarge the valve relief. Could'n you just use a thicker gasket?
Peace bro.

 

[CHINGArider]

The valve reliefs are the indentation on top of the piston to clear the valves. I'll just take a bit more out using the dremel. Its allready got got a thick gasket on there so I dont want to go over board spacing it out anymore.

 

[tubes380]

you got any photos of the piston and how much did you get it for?
also what cc are yo going to have now?

 

[CHINGArider]

you got any photos of the piston and how much did you get it for?
also what cc are yo going to have now?

Sorry dude I got mine off a mate as a "one off" for $70 so I cant help u there. Maybe epod can help u out. And yeh this piston will make it 135cc.

 

[epod]

ESD will have them in couple of weeks.

G'day mate. I got mine in thailand from Akuna. Roost might still have some. ESD said they will have some soon.
Chingarider now I understand. Akuna mentioned this also. It would be great to see a before and after photo of your dremil job.
Ride on bro's.

 

[Mack]

Thanks again fella's. I called retro 50's they told me it is very risky trying to bore these alloy lifan barrel's any further. Retro 50's did not have a gasket for me, would only sell me a complete kit with 56mm barrel japanese piston, $320.

Yeah, is so risky they've done it and will sell to you for big$$$.

 

[epod]

Cheers mac

Yeah mac that's what I figured. I have come to trust the opions of a few guys on this forum, you being one of them, as the photos of your work proof of the pooding. Thanks alot mac your a legand.