Fitting Bandit cylinders & pistons to GSXR1127

[matt]

Hi, having recently done a compression test on my 1127M motor and got some pretty low scores, It looks like I might have to do some work on it.

As a possible budget option, I was thinking about swapping my block and pistons for the ones from a low mileage 1200 Bandit, I have done a search and the general consensus is that the compression ratio will be less. Would this still be the case if I am using the GSXR1100M head?

I am also wondering if I will need to open out the cases slightly to get the Bandit liners in.

If anyone has done it and can advise that will be great.

Cheers

Matt.  

Edited January 19, 2017 by matt

[Swiss Toni]

1127 and B12 have same stroke. So   

Bandit capacity comes from bigger bore. Unless there's loads of room between cases and spigots of 1127 barrels, I would imagine you'll have to open up the top of the 1127 cases. 

[no class]

Are you sure your low comp test is not a result of poorly seated valves ?  Do a leak down test first .

[matt]

I had 130 psi on three cylinders and about 70 on the fourth, which went up to 120 when i put some oil down it.

Even if its a sticking valve on the low one, the others don't look too good:) 

Unfortunately I don't have the gear for a leak down test, but hope to have the valve cover off this weekend to check all the clearances.

[Oilyspanner]

The head volumes of bandits and 1100s are the same, but B12 pistons are flatter, not much of a crown - it's the lack of a crown that lowers comp.  even though the bore is a mm larger - could have the head milled down to bump it up again ?

You're doing the right thing Matt, check valve clearances so you can narrow down what's at fault. Would be good to go a leak down test too - a friendly mechanic ?

[matt]

That's a shame, I was hoping the GSXR head was where the extra compression came from.

I will see what I find over the weekend. Cheers. 

[Swiss Toni]

I'd also go with NoClass and Oily! Leakdown test far more informative than comp. test. 

[Blue]

Leak testers are cheap enough on Eblag :tup:

[matt]

Yes, I've seen some on there, only problem is I dont have a compressor to connect it up to.

Edited January 21, 2017 by matt

[Oilyspanner]

I had a thought Matt , if you have the 'worse case scenario'  - you could fit the B12 pistons / barrels and then fit a dot head to restore compression (could use GSXF750 head, as is cheaper). If you use the 40mm carbs, you could use the M's rubbers, match the intakes to these with a dremel and you'll have a fit engine again.

[matt]

Hi, have seen about the dot heads, but to be honest, by the time I've bought 1200 cylinders and pistons plus a dot head, it will probably have been cheaper to just splash out on new rings and hone my gsxr cylinders. Once I know what the problem is with my engine I'll be able to make some decisions. Cheers.

[matt]

Things are looking up, just done another compression test after warming the engine up (probably should have done that in the first place), readings on all cylinders are now between 150 & 160 psi. The engine has done at least 50K miles, so it looks like all the cylinders are as good or bad as each other.

Hopefully if I get time this weekend I will get a chance to check the valve clearances.

One thing I did find while I was playing around with it were a couple of dodgy HT lead connectors, which probably havent improved the way it's been running. 

[Jonny]

On 20/01/2017 at 7:58 AM, Oilyspanner said:

The head volumes of bandits and 1100s are the same, but B12 pistons are flatter, not much of a crown - it's the lack of a crown that lowers comp.  even though the bore is a mm larger - could have the head milled down to bump it up again ?

This is correct, it's the piston shape.

I did this swap a few years ago on a say what now!? 11. TBH, I didn't notice the difference but skimming the head would bring the compression up.