Topic: CR750 replica engine build help

[NickO]

Newbie here guys so go steady on me!

I'm funding the building of a classic race bike using a CB750 SOHC engine. This will be a serious attempt at building a race winning machine and I want to make sure the engine is both competitive and reliable, (that statement is probably mutually exclusive)? What sort of rear-wheel BHP / torque is realistic and what sort of rev. ceiling is achievable?

I would like some advice on what is the best engine kit to use, (pistons/overbore size, rods, gearbox, ignition, etc.). Any and all advice welcome. I would like to use a self-generating ignition system (no battery) if possible.

If it comes-off I'll keep you posted as much as possible on it's progress!

Thanks in advance guys.

[Sam Green Racing]

There are plenty of people on here that can tell you all you need to know and supply you with everything you need.
You need to give the size of motor and let them know what restrictions are placed on you in your chosen class.
Welcome to the forum, hope you are a lottery winner.

Sam.

[traveler]

talk to "kos" on here.  He owns M3 Racing, and CR750 racing is what he does.

~Joe

[kos]

Newbie here guys so go steady on me!

I'm funding the building of a classic race bike using a CB750 SOHC engine. This will be a serious attempt at building a race winning machine and I want to make sure the engine is both competitive and reliable, (that statement is probably mutually exclusive)? What sort of rear-wheel BHP / torque is realistic and what sort of rev. ceiling is achievable?

I would like some advice on what is the best engine kit to use, (pistons/overbore size, rods, gearbox, ignition, etc.). Any and all advice welcome. I would like to use a self-generating ignition system (no battery) if possible.

If it comes-off I'll keep you posted as much as possible on it's progress!


Please contact me and I can help you plan out your replica CR engine. mark@m3racing.com



Thanks in advance guys.

[lordmoonpie]

There are plenty of people on here that can tell you all you need to know and supply you with everything you need.
You need to give the size of motor and let them know what restrictions are placed on you in your chosen class.
Welcome to the forum, hope you are a lottery winner.

Sam.

+1 to what Sam said - the restrictions on your race class in your country will help determine what you can and cannot do. For example the classic club in the UK will allow you to put 62mm pistons in a SOHC engine but nothing bigger....let us know what the score is locally to you and it may even save you some hard earned $$$

90-100bhp is definitely achievable with reliability and 12,000 rpm, maybe more if you go with one of Mark's engines?

[NickO]

+1 to what Sam said - the restrictions on your race class in your country will help determine what you can and cannot do. For example the classic club in the UK will allow you to put 62mm pistons in a SOHC engine but nothing bigger....let us know what the score is locally to you and it may even save you some hard earned $$$

90-100bhp is definitely achievable with reliability and 12,000 rpm, maybe more if you go with one of Mark's engines?


The engine is for a classic sidecar and in this class there are no tuning restrictions, but we will probably build it so it can be transferred to a solo at a later date!

So I assume the biggest capacity allowed is 760.8cc (with 62mm pistons)?

[kos]

If this helps....the engine in the sidecar that won the Classic Racing Series Sidecar Championship in UK last year was designed and built by M3 Racing.

Mark

[NickO]

If this helps....the engine in the sidecar that won the Classic Racing Series Sidecar Championship in UK last year was designed and built by M3 Racing.

Mark

Mark, was that Brian Gray's bike (Honda) by any chance? I thought a Norton had won the 2009 CRMC sidecar championship (but I may well be wrong)!

Nick

[kos]

If this helps....the engine in the sidecar that won the Classic Racing Series Sidecar Championship in UK last year was designed and built by M3 Racing.

Mark

Mark, was that Brian Gray's bike (Honda) by any chance? I thought a Norton had won the 2009 CRMC sidecar championship (but I may well be wrong)!

Nick


Brian Grey's sidecar.  I might be wrong or have wrong series, but Brian told me he won a championship last year.  Perhaps I heard him wrong?

KOS

[NickO]

If this helps....the engine in the sidecar that won the Classic Racing Series Sidecar Championship in UK last year was designed and built by M3 Racing.

Mark

Mark, was that Brian Gray's bike (Honda) by any chance? I thought a Norton had won the 2009 CRMC sidecar championship (but I may well be wrong)!

Nick


Brian Grey's sidecar.  I might be wrong or have wrong series, but Brian told me he won a championship last year.  Perhaps I heard him wrong?

KOS

Yes Mark,

According to Brian's website he did indeed win a championship with his Honda!

Nick

[lordmoonpie]

+1 to what Sam said - the restrictions on your race class in your country will help determine what you can and cannot do. For example the classic club in the UK will allow you to put 62mm pistons in a SOHC engine but nothing bigger....let us know what the score is locally to you and it may even save you some hard earned $$$

90-100bhp is definitely achievable with reliability and 12,000 rpm, maybe more if you go with one of Mark's engines?


The engine is for a classic sidecar and in this class there are no tuning restrictions, but we will probably build it so it can be transferred to a solo at a later date!

So I assume the biggest capacity allowed is 760.8cc (with 62mm pistons)?

No idea what restrictions are on chairs - at the mere mention of them I come over all sleepy and head for the nearest grass bank...