Topic: Diesel 750

[SohRon]

Today I will be attempting to fit this Locomotive engine (V-12 2-stroke; 750 cubic inches per cylinder) into a CB750 frame. I may have to do some frame modifications to get it to fit, and I may have to lengthen the primary chain to mesh up with the tranny... I'll just have to leap those hurdles as I come across them. I will use the "lay the engine over on its side and lower the frame down over it" method of mating the two together, as I'll be doing the job myself...

Any thoughts?

Oh, and I'll be setting it up as a Cafe racer, so keep that in mind...

[bozo4onion]

What kind of oil will you use synthetic or no?

[bikerbart]

Id go with stock airbox on this one.

[bucky katt]

as long as there are no friction modifiers in the oil. what about an extra wide rear tire?

[SohRon]

I may stay away from the synthetic as it's a two-stroke. I hesitated about putting this engine in a 750 frame (a two-stroke, that is), but I think it will develop some real power on the straight-aways...

Id go with stock airbox on this one.

Good tip! Could be too much turbulance if I went to pods.

[SohRon]

what about an extra wide rear tire?

I thought about that, but I'm going to stick with the stock rear set-up here...

[kpier883]

You should consider a fairing of some sort to direct extra cooling air towards the engine.  A two stroke fires almost every time the piston comes up and therefore your new engine will genrate almost exactly twice as much heat as the original 750 engine.  If the cooling continues to be marginal, consider an oil cooler from a CBX or other acceptable model.  DO NOT LISTEN TO THOSE who said to use Synthetic oil or ROTella.  This engine is a TWO STROKE.  HELLO.  You should use two stroke premix.  Recycled is ok.  I have found that chain saw blade oil is a good substiture.  If you follow my guidelines your new cafe should provide years of service and stands a good chance of winning some awards.  If you need technical assistance feel free to contact me.  I hear Carpy is ok with cafes too, in the event that I am unavailable.  (I have been helping Mr. Cameron (Kevin) with a similar project and have been very busy of late)  A megaphone and some pods will really wake that combination up.  Go up two sizes on your mains with this setup.

[Spanner 1]

DONT use a V-12 motor, you'll be sorry because the one I used in that last Project I did had horrible vibration between 250 and 300 rpm.
I ended-up taking the dang thing out and putting in a P658J V-16.... make sure it's got the 'J' designation, tho' as that's the one that fits the 750 K series frame. Good luck priming the injectors!!!...that's a whole 'nudder Thread!

[Markcb750]

Are you afraid the requirement for larger tires will impact the handling?

[SohRon]

You should consider a fairing of some sort to direct extra cooling air towards the engine.  A two stroke fires almost every time the piston comes up and therefore your new engine will genrate almost exactly twice as much heat as the original 750 engine.  If the cooling continues to be marginal, consider an oil cooler from a CBX or other acceptable model.  DO NOT LISTEN TO THOSE who said to use Synthetic oil or ROTella.  This engine is a TWO STROKE.  HELLO.  You should use two stroke premix.  Recycled is ok.  I have found that chain saw blade oil is a good substiture.  If you follow my guidelines your new cafe should provide years of service and stands a good chance of winning some awards.  If you need technical assistance feel free to contact me.  I hear Carpy is ok with cafes too, in the event that I am unavailable.  (I have been helping Mr. Cameron (Kevin) with a similar project and have been very busy of late)  A megaphone and some pods will really wake that combination up.  Go up two sizes on your mains with this setup.

Thanks for all of the valuable advice! +1 on the synthetic oil in a two-stroke. The chain saw oil sounds promising; I'll look in to that. I will, of course, be using three 750 carb assemblies (12 cylinders=12 carbs), so the advice regarding the mains is helpful. And the only fairing I have is an old Vetter I may be able to modify...

Are you afraid the requirement for larger tires will impact the handling?

Larger tires??? You don't think the stock set-up will work?

Edit: after giving it some thought, I decided you were right about the larger tires and found these:



I'm hesitant to go to larger tires as I'm not sure my wife's feet will still touch the ground when she's riding the bike if I do, but the added weight requires it, I guess. That will mean extending the forks and the swingarm. Shorty shocks will probably make up the difference, though...

[kopptl]

gonna need a crane!! have fun getting it off the side stand, probably need a crane for
that to, ya might just drop a nut... lol

[SohRon]

gonna need a crane!! have fun getting it off the side stand, probably need a crane for
that to, ya might just drop a nut... lol

Not sure what a turkey-sized Asian waterfowl can do for the project, but if you think I'll need one, well, I guess I'll have to contact the zoo...

DONT use a V-12 motor, you'll be sorry because the one I used in that last Project I did had horrible vibration between 250 and 300 rpm.
I ended-up taking the dang thing out and putting in a P658J V-16.... make sure it's got the 'J' designation, tho' as that's the one that fits the 750 K series frame. Good luck priming the injectors!!!...that's a whole 'nudder Thread

Don't know how I missed this post earlier, but it seems like sound advice. I know the "J" series are smoother and quieter, but I don't have another set of carbs for the extra cylinders, so I'm sticking with what I've got. Priming shouldn't be a problem after I get the gantry system set up...

[CB500_k2]

I fear that it will be a bear to kick start.  As a two stroke v-12 it will sound great over 10000 rpm.  That and the magnificent cloud of black soot will be really impressive.  I would go with a 12 into 12 megaphone exhaust system.

[SohRon]

I would go with a 12 into 12 megaphone exhaust system

I was thinking about that, but I kinda like the sporty looks of a 12 into 1 exhaust. Anything to achieve the sleek look of a racer, you understand.

[mick7504]

Back to basics if all else fails. 

[HavocTurbo]

I would go with a 12 into 12 megaphone exhaust system

I was thinking about that, but I kinda like the sporty looks of a 12 into 1 exhaust. Anything to achieve the sleek look of a racer, you understand.

Most racers had individual exhaust back in the day. 12-12 6-6 16-16 and so on. Made it easier to tune each cylinder.

How may carbs you going to run? 12? 6? 3? If you need help with a manifold or routing the exhaust let me know.

Also.... Might want to think about carbon fiber fairings... much lighter and withstand the heat that 2-stroke will put out.

[domer]

hmmmm, self induced infertility.... boil your nutz!!!!

[Markcb750]

How may carbs you going to run? 12? 6? 3? If you need help with a manifold or routing the exhaust let me know.

Otto is amused

[Rampage1967]

I fear that it will be a bear to kick start.  As a two stroke v-12 it will sound great over 10000 rpm.  That and the magnificent cloud of black soot will be really impressive.  I would go with a 12 into 12 megaphone exhaust system.

May I suggest using A CB360 twin as a starting engine??

And, I vote for 12 into 12 for the pipes.

[BobbyR]

I would suggest the 630 chain on this bad boy.

[wannabridin]

i would suggest a nice 12-1 with a good 12" tip, maybe 14".  def. need to run a good baffle though, i don't want you to hurt anything with too little backpressure!  you should make the exhaust underseat!  that will clear up some extra ground clearance in case you start to get really ballsy in the twisties! 

and i say you keep the stock centerstand.  shouldn't be too difficult to get up on there with these slight mods

[HavocTurbo]

I would suggest the 630 chain on this bad boy.

Maybe a double chain set-up from cycle x?

That'd look badass. 

[SohRon]

Lots of great suggestions, and I appreciate the offers of help!

How may carbs you going to run?

After much consideration, I'm thinking that, since each cylinder is 750cc, I might have to run a separate 750 assembly per cylinder in order to maintain the correct flow... just gotta figure out how to mount twelve airboxes. Pods are starting to look more and more promising, though it might be a bear setting the jets on 48 carbs...

And, I vote for 12 into 12 for the pipes.

I'm a little concerned they might affect the wind resistance profile... we want it to be as sleek as possible; that's why I decided to mount the engine lengthwise rather than transversely across the frame, though it will make for kind of a long reach for the Clubmans...

May I suggest using A CB360 twin as a starting engine??

Great idea! That solves the kick starter problem, too!  I knew I was coming to the right people!

i say you keep the stock centerstand.  shouldn't be too difficult to get up on there with these slight mods

Couldn't work on it without one! 

[moham]

Larger tires??? You don't think the stock set-up will work?

Edit: after giving it some thought, I decided you were right about the larger tires and found these:

Do these not come in white walls?

[SohRon]

Larger tires??? You don't think the stock set-up will work?

Edit: after giving it some thought, I decided you were right about the larger tires and found these:

Do these not come in white walls?

Whitewalls would just look gaudy, IMO. Jeeze, man... show some class!