Piston/Head/Valve specs between CB,CA,C & CS

[VegeKev]

G'day Everyone,

Time to freshen the C92 engine up (I do like the look and smell of blue smoke, but...) and I'm wondering if someone can definitively tell me what is possible:

I'm thinking of using CS92 pistons, though I'm open to CA or CB possibilities , but I'm not sure if the C92 combustion chamber can handle the increased piston height? (as an aside to this, the CS92 pistons are being advertised as the same as CB93 pistons....is that right or another eBay boggey?)

Was there any difference in valve head diameters between the C/CS/CA/CB?

Also wondering what possibilities exist with regard to cams, especially if I go with the high comp pistons?...am I going to run into piston/valve clearance problems?

Also wondering if the crankshaft (no centre support) will stand up to the increased workload?

I know this is probably a bit of a loaded question due to the amount of 125 models/engines that Honda created .....but I thought this would be the place to ask.

Kev

[Sam Green]

Kev, can you post some pics of your bike.
Bike from both sides, engine from both sides and a close up of the crankcase below the carb.
Does your motor have a breather from the top engine mounting/cam box cover?

The combustion chamber on all the 92 series are the same as are the valves.
CB92 pistons will fit without issues and the lift on all the cams are the same, just duration and opening and closing times are different but nothing touches no mater what combination you use.

If you do indeed have a 2 bearing crank, if it's the same as the C95 it will stand up as good as any 3 bearing one.

Sam.

I think I might have some new C92 pistons but not sure on rings and pins. Will look when I go home for lunch.

[Sam Green]

Kev, I've got a set of new CB92 pistons if you're interested, they are +0.25mm.
They have been in a motor but were never run.

Sam.

[VegeKev]

Hey Sam,

Sorry for the delay in responding...been away for the weekend and didn't have web access.

I've attached some photos, hopefully they will show what you need to see.

Excellent news to hear that I can play with the internals a bit

And Yes, very interested in the CB pistons....PM me and I'll get some $$$ transferred

Do the wrist pins (I call them gudgeon pins!) usually wear enough in 30k to require replacement?

Thanks heaps for the info, makes this sort of work far less stressful to have a knowledge resource like yours available

Kev

[Sam Green]

Hi Kev, the reason I asked for the pics was that models seem to vary a lot depending on what country they are destined for.
I had never heard of a C92 with a two bearing crank and just wanted to be sure of what you had.
Apart from the seat, rack and silencers, your C92 looks just like the UK spec bike which had a 3 bearing crank and from the pictures, I can assure you that your motor has a 3 bearing crank.
The piston pins don't normally go in that mileage unless starved of oil but a lot of motors would need a rebore by then anyway and the pins would come with the new pistons. (are we talking Kilometors or Miles?)
The CB92 pistons I have have pins and rings and you will just need to get some clips. (I may have some, will look at lunch time)
I took the pistons as payment for a motor I built for a mate so they stand me at £38 (British). I'll parcel them up and get a price from the Post Office this afternoon for the shipping.

Sam.

[VegeKev]

Hey Sam,

Thanks for the info...I'm not surprised I had it wrong...

I thought the earlier models had the 2 bearing crank...happy to have the extra support for the extra super fast ninja turtle CB internals The speedo is in Miles and the seat and rack are as I received her. The pipes are Thai ebay specials.

With regard to cam timing, have you ever come across a vernier cam gear that would fit a Benly motor?...be nice if I could get my hands on one so I could easily play around with the timing . I'm thinking that these engines have no problem revving so maybe retarding the cam timing a tad to bump the lower end torque up?

If you had to pick a cam for the beast, which one (from what model?) would you choose?...

Cheers,
Kev.

[Sam Green]

There isn't a specific cam wheel Kev, I altered one to give half a tooth, It knocked the top end down to 9,000rpm but the lower end was great, but saying that, it was out to 175cc with tons of compression.
Best cam for your application would be a late model CA95 cam without the rev counter drive and the CA95 carb to go with it. That would then give you full CB92 spec.
Pistons will be on their way as soon as the PO opens (about 3 hours).

Sam.

[VegeKev]

Hey Sam,

Sweet!.....I'll start looking for a tacho-less CA95 cam straight away.

I was that thinking that modifying the cam gear would be the easiest (did you modify the gear hole and make a special locating dowel....or....:confused )....another job that should be interesting

I've got a set of CB93 dual carbs on their way to fuel the beast....just have to learn how to modify the throttle cable to suit the slide instead of the rotary type....never played with swaging cables before.

Also thinking of setting a couple of new header pipes up with EGT's to make sure I don't drown or melt anything ....

Thanks again,
Kev.

[Sam Green]

I just elongated the holes until they were half a tooth distance.

Sam.