1100 Performance engine rebuild

[Circo911]

Ladies and gents, I'm new here so hello and thanks in advance for the comments.
I've just had a problem with my 83 GSX1100 Kat. It looks like the cam chain tensioner nut had worked loose, the chain slackened way off and then she just stopped. Sounds like its dropped a valve or 2 (i hope) but it's in the process of being striped to check. Whilst its apart I'm thinking of some upgrades to get the engine performance a little closer to modern bikes. I reckon I'll be happy with around 120hp, more would always be better but I'm not a racer so needs to be usable around town, I like the way the way the power is delivered at the moment so I'd like to keep that aspect as much as possible.

I'm considering a re-bore, fast cams and some over sized valves, but I've no experience of this kind of work. It's already got 34mm rs mikuni carbs and a yoshi racing exhaust but the engine is completely standard at present.

Any tips or suggestions would be very much appreciated.

[johnr]

aye, tuning the kat motor requires deep pockets! im recconing that a decent head job assuming its not mullered by dropping valves, with new valves and seats, possibly guides, 3 angle
valve seats and a gas flow wont leave you much change from a grand by the time you factor in gaskets camchain a manual tensioner and two lots of postage, 1170 kit comes in at 500 quid at least, plus the cost of boring the pots, youd really want to upgrade the clutch basket and plates/springs, and that doesnt come cheap. that might get you 120bhp, but a set of rs36 carbs will set you back 5-8 hundred if you can find some, then you might want a more precisely controlled ignition, higher output coils and heavy duty leads. suddenly youve spent 2.5k and are making the same horsepower as a stock bandit 1200 engine which would cost you 400 quid and weigh 20 kilos less.
im not saying dont do it. i am however saying go into it with your eyes open and your expectations set to 'realistic' these bruising motors can be made to make decent horsepower, but they will require a lot of money thrown at them to do so.

[stockcar]

drop a later "EF" 1135cc lump in the hole - did this on my EZ approx 25 years back and was mental

with the 'wrong' carbs it did 106bhp at the back wheel on a local race dyno

[johnr]

but finding an efe engine is a problem all of its own. everybody wants one and nobody is selling. however, bandits are still relatively plentyful and as such are cheap.

[FBJ]

Hi hows things, welcome to the Kat owners club. I've built a few Kats which have made nice power.
1170 kit will cost £500 ish with the rebore, it will improve midrange grunt even on a stock bike, however harder to start when hot as it ups the compression. GSX1100EFE starter and gear sort that problem.
A clean up of the valves and a nice head flow (£300) along with the 1170 will probably get you 120 hp. Personally i'd go with 36mm carbs if you want a bit more power.
EFE cams will give a little power gain.
Mild cams £300 and bigger valves £600 fitted will give you 130hp plus. We had 130hp on my wifes with stock valves

[Circo911]

Guys thanks for the tips. I'm budgeting around £1500, keeping the carbs and exhaust. Ignition is already upgraded, as is the clutch and it's got got an over sized oil cooler fitted. I've been told about a complete Yoshi kit you can get with big bore pistons and fast cams which is what i'm leaning towards. Sounds the simplest option. Any one just done those mods? If so I'd be interested to know what kid of gains are seen.

Here's the bike.

[Uncle Bob]

Look at FBJ post above your last one Circo911 as I moved it from another thread, but it didn't go at end - UB

[Circo911]

Uncle Bob thanks, that's just what I had in mind. How much extra HP would the carbs give based on just going 1170 standard valves and efe cams? For £300 i might as well put the cams in. I'd looked at over sized valves but at £50 a valve they might push the budget.

[Circo911]

Cheers Blix, just sent him an e-mail.

[Bikeazoid]

What is the EFE motor? Is that from the bandit? 1200?