Topic: Help with pistons for a CB160 race bike

[Kickstart]

I realize it's not a four cylinder... but it's still a SOHC... and this is best forum (IMHO).

Anyone have any suggestions on where to get 0.75 or 1.0mm over pistons for CB160?

I've got an 1965 CB160 if rough shape that my friend and I are trying to build to race in USCRA F-CB160 and the AHRMA LeMans start CB160 classes.  Upon tearing down the engine we found heavily scored 0.5 pistons... so we need to go to 0.75 or 1mm.

Bill Moeller for Bore-tech wasn't able to source any for me so I've been eyeing some on eBay, but I'm hesitant to buy stuff from Thailand.  Anyone purchase "NOS" pistons from Thailand on eBay... and if so were they really NOS Honda pistons?
http://www.ebay.com/itm/360932509447
http://www.ebay.com/itm/310611390162

I'll also try posting in the wanted section.

Thanks,
Chris




 

[bwaller]

Please don't take this as support for that seller, but just last night I spoke with a fellow member of our race ass'n who praised someone from Thailand that he bought Yamaha parts from directly. I've ended up with new Honda parts in genuine Honda bags marked "made in Thailand".  Those shown are ART pistons.

What is the piston diameter?

[Kickstart]

Per the shop manual, 50mm diameter, so I assume 50.5 for the ones currently in there.

I was under the impression that ART may have made the OEM pistons for Honda back in the 60's... so I thought it could be possible they're still OEM.  Maybe that's wishful thinking on my part

That said, I thought ART pistons were good quality (don't recall where I heard that though)... assuming those on ebay aren't knock-offs.
I don't necessarily need Honda OEM, but I do need something good enough to race with.

CMSNL only has one 0.75 and one 1.0 left... but one of each probably isn't going to work out

Thanks,
Chris

[bwaller]

For sure ART was Honda's piston supplier, and the quality speaks for itself.

[Kickstart]

What do you think the chances are those pistons on eBay are the "Real McCoy"?

Do you know of anyone who purchased fake ART pistons in fake Honda boxes... or maybe a better question would be, is there a non-destructive way to verify they're the real deal after I purchase them?

Thanks,
Chris

[bwaller]

I don't know anyone stung with fake junk, and they look like the real deal. But sorry man I know that likely doesn't put your mind to rest.

[Kickstart]

Actually, that's a big help.  The one seller has a lot of positive reviews, and it's conceivable he's collected or bought out NOS from Honda dealers in the country.  Ebay also has a pretty good guarantee policy these days.

Additionally, my local machinist is semi-retired with a lot of experience working on older Japanese bikes, so I assume he'll be able to tell if they're cheap knock-offs or the real deal.

Thanks!

[turboguzzi]

have you tried to look into all sorts of small bore honda piston kits?
tkrj has this excellent ref page according to bore, click on the specific piston for details like pin dia, etc.
http://www.tkrj.co.jp/product/m-piston-kit.html

i already see there a 50.5 CB100 slug....

[Sam Green Racing]

Chris, I'm not sure if your class has a upper capacity limit but I think the 52mm CB175 piston will go in and at a guess, will raise the compression some.
I know a member who fitted them and beside a Mike Rieck head job and a Megacycle cam, won first time out.
Plenty on Ebay at sensible prices, here's a pic.

[bwaller]

I believe this is a stock engine class so 4th oversize max??  Often we're allowed 1mm or 5% overbore but I don't read that in the USCRA rule book for this class.

[Sam Green Racing]

Thanks Brent. I'm not sure which class the guy I mentioned ran in and I can't remember his user name on here.
His real name is Gene Duffy and he was at Mikes when I was there.
His bike was a CB160 bored to 200cc and it was really slow and he finished last in most races.
After Mike finished the motor it won first time out.

Sam.

[bwaller]

I'll let Kickstart speak to his class choice but there is both a 160 stock class as well as a 200 class.

[Old Scrambler]

.............and a few (lot of 'cheatas'.............

BTW.........upgrade the suspension with CB200 forks and trees.........

[Kickstart]

Thanks for the help guys.

Yeah... from the little I've been able to find out, the rules are different from the USCRA and the AHRMA cb160 LeMans start race classes.  Technically it's an exhibition class for AHRMA and I don't believe they list any rules in the handbook (at least not that I could find). 
Big Bob was able to put me in touch with an experienced AHRMA cb160 racer who told me the AHRMA "rules" for their LeMans start is the same as the 200GP class, but limited to either a CB160/cb175 bike.  So my understanding is you could bore the bike up to 200cc and do whatever porting, and still be legal in their LeMans start.

USCRA is a lot more explicit with their their rules for the F-cb160 class. I don't even think cb175's are allowed.

BTW - has anyone noticed the updated USCRA website this year?  It's looking really nice, with clear links to useful information. They even put together a handy one page calendar with of all the regional race events - including the VRRA races:
http://www.race-uscra.com/uploads/2/9/7/5/29751819/2015_vintage_calendar.jpg.jpeg

i was about to send the head off to Mike for porting and oversized valves, but since USCRA is relatively close to me I decided to leave it with stock size and not port.  Kind of a bummer, as I'm going to be totally outclassed when I race it with AHRMA. I know I don't have the skill yet to place in this highly competive class... but I don't want to be the guy holding up the next race either

Speaking of forks, I'm having a heck of a time finding the later year front forks.  I've got the older style steel fork lowers, and you can't get fork seals for them anymore.