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Boring out - CBR900

Matt21 - 27/5/14 at 12:00 PM

I've been looking into getting some engine work done.
I'd like to stick with the cbr 919 engine (or buy a 2nd 893 to do the work on) but would like to get it bored out

I've found a place that can get it to 974cc

but theres no info on what gains you actually get, can anyone give me an idea?

(im not after people telling me its a waste of money etc etc)

but if there are any real reliability issues i wouldnt mind hearing about them too

cheers!

[Edited on 27/5/14 by Matt21]

carpmart - 27/5/14 at 03:27 PM

Ive raced with this engine for six seasons. Several people in our championship chased power (cheating in the process) a few years back. They got quite good results, Damien at Daytuner did a few for the guys. The problem is that you go from ultra reliable, as the 919 has proved itself (except the gear box) to pretty unreliable. People have swapped out the exhaust or inlet cam(forget which one) for an exhaust or inlet, which seems to give give both extra lift and duration. I've also tried running the 900 on a CBR600 CDi unit which gave me a 1k plus extra revs and a slightly more torquey power delivery.

HTHs?

twybrow - 27/5/14 at 03:40 PM

I am not saying it is a waste of money - it is your money, you should do as you see fit. But I would be interested to hear why you are going down this route, rather than going for a larger cc engine as stock? Would an R1/GSXR not give you similar outputs but more reliably/cheaper? Is this for a specific race series?

Matt21 - 27/5/14 at 03:57 PM

It's not for a race series no, just for road use and trackdays, eventually sprints/hill climbs. More as a bit of fun than anything else

as for just using a bigger engine, it would be nice, but believe it or not, I can get a 974cc a lot cheaper but.... if its going to be unreliable as carpmart says then it would be more hassle than its worth

any idea on how much extra power i would get? i found one article that said around 15bhp with a 945cc kit, so im guessing maybe 30bhp extra?

do you have anymore info on using the cbr600 cdi? is it just a plug and play? no negetive effects?
and as for the valves, is that something worthwhile for me to look into on a standard engine? again any negetive effects?

drt - 27/5/14 at 05:07 PM

I suspect you're getting the 974cc big piston kit from a good manufacturer,
so the mass would be equal to the standard.
So shouldn't be less reliable
Thermal household can suffer...
But you're better of asking the manufacturer of the big bore kits,
as most builders will just go for the other bigger std engine

Horsepower gain...
Without increasing your cfm the gain will be quite small.
Torque will benefit

bigger valves, maybe cams and flowing the head
will do a lot of good.

A cbr600 cdi on a 900? Can't say I heard about that.
But the 600 revs higher(limiter) , so mind that dash

MikeRJ - 27/5/14 at 05:48 PM

quote:
Originally posted by Matt21
It's not for a race series no, just for road use and trackdays, eventually sprints/hill climbs. More as a bit of fun than anything else

as for just using a bigger engine, it would be nice, but believe it or not, I can get a 974cc a lot cheaper but.... if its going to be unreliable as carpmart says then it would be more hassle than its worth

any idea on how much extra power i would get? i found one article that said around 15bhp with a 945cc kit, so im guessing maybe 30bhp extra?

Absolutely no chance on 30bhp without a lot of additional work, and 15bhp extra just by going from 918 to 945 is pure fantasy (12.7% power increase from a 3% displacement increase?).

Have a look at the dynobike web site. They managed to squeeze about 25bhp from a big bore kit, but that's after porting the cylinder head, machining to get the correct CR, re-jetting the carbs and with a decent performance exhaust. One and a half to two weeks work and $3000.

In terms of value for money a second hand 954 will look like a bargain, and give you more power.

ReMan - 27/5/14 at 06:31 PM

Not to poo poo it from a fun excersise point of view, and mine is an 893, but I remember back to my moped days when you could get a 50-65cc BIG BORE kit!
I just could not believe the difference would be sufficient so with more entertaining things to buy when I was 16 I kept my money in my pocket!

mark chandler - 27/5/14 at 06:31 PM

Just stick a turbo on it

I,ve turned the boost up since this was done, engine is big standard apart from lockup clutch.

sam919 - 27/5/14 at 06:39 PM

Have you chatted to AB about getting some more ponies by jetting etc, not a lot but you also get a smoother torque curve.

M.CH, have you done anything to the box for the extra bhp?

mark chandler - 27/5/14 at 06:45 PM

Engine is as it was dragged from the bike, on the basis that a replacement is Ł400 -Ł500 it's not worth pulling the head as gaskets add up.

I do have a spare box, just back off when notching it up a gear and use the clutch on the way down.

It has plenty of torque so you can leave in a high gear and belt around, car needed a 3.14 LSD so factor this in.

sam919 - 27/5/14 at 06:56 PM

Cool, are there any recommendations for beefing things up say for track use?

mark chandler - 27/5/14 at 07:31 PM

I just fitted harder springs and fully rose jointed the suspension so I could set it up properly, then stuck on Ł15 second hand slicks for much cheapness.

You need to run 13" wheels really, I have 6j with 185/60/13 on the front with 7j 205/60/13 on the rear, these cars drive around most things on the track anyway.

Car also runs an oil cooler and accusump to help contain heat and oil surge.

[Edited on 27/5/14 by mark chandler]

MadMaxx - 28/5/14 at 05:51 AM

Is it realistic 150 bhp declared from someone simply dynojetting and with a good exaust?

MikeRJ - 28/5/14 at 06:19 AM

quote:
Originally posted by MadMaxx
Is it realistic 150 bhp declared from someone simply dynojetting and with a good exaust?

Certainly not from a 918, and I think would still be optimistic from a 954.

carpmart - 28/5/14 at 07:55 AM

I managed 119.3 bhp at the wheels with a chain driven drive in my race car with a 919. It was correctly jetted with original airbox (K&N) and a not perfect exhaust system. Optimized fully I would guess 125 bhp is the max you can get from a standard engine.

MadMaxx - 28/5/14 at 08:34 AM

Just to compare with the official figure of 128 bhp, at the fly wheel I suppose, what will be yours? 135 bhp and 140 fully optimised?
I have standard airbox with K&N with the airbox partially cutted to directly expose the filter to the air and don't touch the bonnet, so I should expecting the same power?

Matt21 - 28/5/14 at 08:52 AM

I spoke to Holeshot racing, which is who I would be using

he claims 12ftlb and 20bhp

eitherway, I dont think I would be going ahead with it as I do a lot of miles and the engine wouldnt be used as it would be built for.

sam919 - 28/5/14 at 10:36 AM

The purity of the caterham fireblade in its original form is excellent a few bhp won't make much difference, its a bullet proof wee engine and in a high state of tune per cc , you'll enjoy it better in the long run keeping it standard...

Doctor Derek Doctors - 28/5/14 at 08:54 PM

quote:
Originally posted by Matt21

do you have anymore info on using the cbr600 cdi? is it just a plug and play? no negetive effects?
and as for the valves, is that something worthwhile for me to look into on a standard engine? again any negetive effects?

I'd also be interested to hear about the CBR600 CDI unit change, any more details?

mark chandler - 28/5/14 at 09:03 PM

You can also mod the ignition pickup for a little more advance which gets a bit more power running on optimax, these are designed to run on 93ron fuel. Modified back plates used to appear on eBay for this a few years ago.

[Edited on 28/5/14 by mark chandler]