Hello & crank symmetry

[bikerphil]

Suppose i better say hi before i go asking questions....
Hi folks

Don't a have a VTR, But i'm considering using the VTR engine as the base for a nitrous drag racing machine.
Maybe one of you just happens to know this, or if not, has a spare crank lying around and could do some measuring and find out.
Is the VTR crank symmetrical?
In that - are the bearing journals the same at each side and are the camchain sprockets the same distance from each journal? Basically, i want to know if i can put one in backwards?

You might be thinking that sounds odd, and it is ....

[tony.mon]

That sounds fun.
I've been playing for a while with these engines; and a Big Bang version is also possible, may be very useful on a drag bike.

I have a spare crank or two, can dig it out on thursday, photograph and measure for you.

You'd have to use a different drive for the oil pump and water pump, but electric ones would be possible.
Also of course, the primary drive would also need to be mounted on the other end of the crank.

Were you planning FI?
One potentially easier option is to use a varadero motor- it's essentially the same cases and all of the parts are interchangeable, but the later ones are fitted with all of the sensors for FI, although the throttle bodies are too small to be of any use.

Perhaps more than just an afternoon's work.....

[bikerphil]

Tony - Funny that i've just spent 15 mins reading your engine rebuild thread, then when i came back it was you who'd replied.
What i was hoping could be possible is to mount 2 vtr engines side by side, one with the crank in the wrong way and a splined spacer tube connecting the 2 cranks. So it would effectively become a 2000cc v4.
I would like to use carbs as flat out is the only required throttle position.
Cheers

[tony.mon]

Why not just do the easy thing and fit one in front of the other, like a fair few drag bikes, nortons, vincents etc?

Chain run would be the problem your planned way- to get the engines balanced the output shaft would be 400mm or so at least too far outboard, you'd need jack shafts, and that costs power.

But broadly, yes, I think it could be done.
Ignition pickup would also need to be relocated/remade, by the way, maybe though you could time the pairs of cylinders to fire simultaneously, and just a better coil needed to fire two at once.

FI would be to get the nitrous set up to alter with boost, these don't have any Power Commander options that are simple to fit/use.

Whereabaouts are you?
I have some parts that might be of use, cases, cranks etc.

[bikerphil]

The reason for even thinking of this idea was because i'd seen a pic of a vtr bottom end in bits and was really surprised how narrow it was. It was an SP1 bottom end which i think is even narrower than the VTR? Anyway, i figured 2 of them side by side, with all ancilaries, flywheel, clutch etc removed would be not a lot if at all wider than the GSX1100 i'm currently using.
I wouldn't likely use the vtr clutch or gearbox, just the casings and cranks. Ignition would be MSD and fire all 4 cyl off one end of the crank like any inline 4. The reason for turning the crank round is to connect the splined ends together rather than use the splined end of the left engine and the tapered end of the right one, which would likely slip and make a mess. Like you say, driving the oil pump would require a workaround, but i'm not familiar enough with it to visualize a solution. In fact, the crank is the only bit i've looked at!
Nitrous would be a wet system as thats what i'm familiar with.

I'm in lancashire. It is deffo just at the fleshing out ideas stage, but without seeing one it's hard to see solutions.
Cheers
Phil

[seb421]

I love it when boffins talk engines phwarrrrrr

[bikerphil]

I love it when boffins talk engines phwarrrrrr

i never got anyone exited with engine talk before .... i feel dirty now

[tony.mon]

OK, I get the idea better now.
I think you could do this, but then the reversed engine would run in the reverse direction, too.
The cam timing would need to be completely revised, but the crank and pistons would be fine.
Cam sprockets are able to be slotted, so they could be dialled in.
Possibly the oil pump could be solved with a jackshaft, to reverse the normal direction of rotation back to the way round it should travel.
Lastly the cam chain tensioner would be on the wrong side of the chain, for both cylinders, acting on the non-tensioned side of the chain run under acceleration.
The head castings have an option of being machined on either side, so those could be remachined on the other side of each head and the old holes blanked off.

Apart from that, I can't foresee major problems, apart, of course, from actually getting the lumps mounted in a frame, and timinging them to behave as a single engine, and I'd also suggest using two separate airboxes.

[bikerphil]

Tony - you can tell when someones spent many hours rebuilding the same engine as thats the only way you become familiar with the little nuances like that.
I think you may have misunderstood my idea slightly, or are over-complicating it. OR i've missed something and just haven't clicked myself yet lol.
I've done an over simplified sketch, which may explain it better. the dark gray bit would represent the lower crankcase half - i've missd putting the layshaft and mainshaft in there to keep it simple. As you can see they both face the same way, i just want to put the crank in one of them the wrong way round so that the splined ends face each other. They will still both spin the same way, and all valve gear, camchains, tensioners etc are normal..... ish.

The blue bit is the splined tube idea that would connect the 2 cranks. this may also double as the primary drive, i could cut teeth on the outside of it and have a wide toothed belt connected to an external clutch and gearbox.
It's a major undertaking ....

I noticed that one main journal has an oil way cut into it, i'm guessing that feeds oil to the big end? if that journal were at the other side of the casing is the oil supply to that side the same?

Cheers
Phil

[gissmo50]

This idea makes me all warm inside, very cool I have a vfr400 v4 and thats fun a 2000cc v4 would be insane fun

Sent from my R800i using Tapatalk

[tony.mon]

Here's a picture of the lower crankcase half:


Copy the picture to a new tab and you should be able to scroll about to see both journals.
As you can see the oil feed holes are not symmetrical, and so a little work would be needed, as well as fitted the journals in the opposite sides.

Haven't got a picture of a crank to hand, but from looking at the bearing shells, they seem to be equal widths, so the crank should fit.
I should be around at home tomorrow afternoon, so I'll dig one out and photograph it.

[bikerphil]

Thanks for the picture dude, what would be useful is if you can place a steel rule in the shot so i can get an idea of the sizes of things.
The only difference between the journals looks to be the size of the oil feed holes, restricted in one side and opened out in the other, is that right?
In which case it might be a matter of drilling them larger on the other side and inserting restrictors in the original side.

If anyone is interested, my current drag bike, and it's entire build can be seen in the archives of my blog site here http://gsxbopchop.blogspot.com/

It's looking more and more possible

I then need to figure out what scope there is for getting more power from the engine, theres no point in using it unless each motor cam be made to produce 150hp NA and strong enough to take another 100hp of nitrous. 400 would net low 7 second times or even 6's if weight can be kept down.

[rob...]

i think you'll find you need billet cranks for that sort of power?? didn't the moriwaki race team have problems with snapped cranks and had to go billet?
or use sp1/sp2 motor instead?

tony??

very interesting idea, i started a similar project with 2 st1100 honda motors, in line. i do like playing with engines. i've had an rf900 out to 1150 and a 1340 bandit in the last couple of years.

[tony.mon]

Thanks for the picture dude, what would be useful is if you can place a steel rule in the shot so i can get an idea of the sizes of things.
The only difference between the journals looks to be the size of the oil feed holes, restricted in one side and opened out in the other, is that right?
In which case it might be a matter of drilling them larger on the other side and inserting restrictors in the original side.

I then need to figure out what scope there is for getting more power from the engine, theres no point in using it unless each motor cam be made to produce 150hp NA and strong enough to take another 100hp of nitrous. 400 would net low 7 second times or even 6's if weight can be kept down.

AndI'm still chasing 10's
The oil feed drillings in the cases would also need to be man enough to feed the newly-enlarged journal, no idea it you can get to those, but probably. Depends if the crankcase uppers are cast as a single unit or several sections machined and then connected together as to whether you still have access to those oilways.

The weakness on these engines and the usual bar to developing high HP/torque is the fact that the swingarm pivots off the back of the cases, without bracing and lots of work the back of the gearbox snaps off due to fatigue.

That's not a problem with what you're planning.

But you can't use high comp pistons as an easy power-up, if you plan Nitrous, so head work, cams, exhaust and big carbs would be the way to go.
For the use you have in mind you can dispense with trying to make it tick over, or pull away from traffic lights cleanly, etc etc and so the tuning can be much more focussed.

I have an idea to improve exhaust gasflowing by chopping a section of the heads out and re-welding, so that the ports exit more cleanly into an oval collector/header before they go into the downpipe.
Looking at the Storm versus SP1 porting designs, this seems to be where a fair bit of the power difference has gone.

Sadly, by the way, you can't use SP1 cams, different diameter, and you can't transplant SP1 heads on either, so maybe starting with two SP1 bottom ends would be better, but a lot more expensive...


Bottom end should be fine, but welding crank pins might be a sensible precaution- if you get a problem it will likely kill both cranks if they're linked as you propose.

[bikerphil]

It seems this idea has come to an end. Technically it would seem it could be done, but i've spoken to someone who has famously raced and does tuning work on these engines and they advised against it, as the crank (which is the main bit i'm using) is very prone to failure at the camchain sprocket radius.
That pretty much finishes it for me, as thats a common fail point on a lot of high power engines. It was a good idea whilst it lasted. And still a good idea perhaps if you were going with near stock power levels. But then, thats not the idea when drag racing!

I'll say, thanks a lot to those who replied, and Tony in particular for your help, knowledge and the pictures. If you wanna build that tandem engine VTR and need any help just email me lol.

Cheers
Phil