Suggest on engine head modification work of 81' GSX1100EX

[Addy Leung]

Hi GS Rider,

I need some suggestion on Engine head modification work of 81' GSX1100EX.
I am interesting to upgrade my 81' GSX1100EX (16 valves, only 3 left in Hong Kong) to a 1260cc with modified engine head(that is what I have learned from internet). I have already collected two necessary used parts for this small project: 1- pair of Web cams 168, 2/ Keihin 37mm RC special carburetors. Also, I have contact Wiseco and ready to order the power package of cylinder block with pistons(10.25:1, 1260cc) for daily street purpose.
But in fact, I have no experience in dealing with modifying an engine head and it is the first time. Beside, there is no such modification-engineering workshop for engine head in Hong Kong. Therefor, I looking for oversea service or just buy one from oversea.

In my mind, I think the following item may be carried out to the engine head but I don’t know which item is a must item to be carried out & how extend it should be for daily street purpose. It would like to have your help to give me some further professional suggestions.

1/ Porting the in/out port (didn’t know how extend should be)
2/ replace all in/out valves with larger stainless steel valves (didn’t know what over size should be)
3/ replace all valve seat, guide, spring, retainer, & seal. (e.g. new bronze valve seat & guide)
4/ multi angle valve job if necessary.
5/ Install my existing spare Web cams 168 in it and adjust the rocker arm clearance.

Any good experience member would give me some advice?
Any good workshop in USA suggested that I could send it to for such service? How about Star Racing? I contacted them, they have good customer service.

Thanks for your help!

Addy

[Billy Ricks]

Have the manifolds for the new carbs matched to the ports. With the new cams I don't think oversize valves are necessary. But if you have some needing replaced it's as good a time as any to do it. You need to think about having the rockers welded and reground too. Check with A.P.E., Cope, and Murdoch as well.

[Billy Ricks]

http://www.headsup.dragbikecentral.com/about.html

This guy used to post here years ago. He has a good reputation.

[Addy Leung]

over size valve og GS 1100?

Bily,

Thanks for your information.
The adaptor of the carbs is not fit to the manifolds, so I find a workshop to make 4 new simila adaptor but a bit smaller and fit to the exsiting maniflod.

Start Racing suggest 19mm intake valve and 24.5mm exhaust valve, but why not 29mm & 26mm(in-out)?

Addy Leung

[Dink]

The valve sizes you quote sound wrong, as a general rule inlet valves are always bigger than exhaust valves.
I believe that 29mm inlet and 24.5 mm exhaust would be about right for your motor.
However have you considered the rideability issues that a "race" motor will raise in such an urbanised environment as Hong Kong?You may find that a milder "optimised" motor may be a more usable proposition in the traffic you find yourself in.
By all means go with the 1260cc kit but how about just dialing in your stock cams fitting a jet kit and a 4 into 1? this will provide you with a tractable and usable "grunt" motor, instead of a peaky pig.
Dink

[Addy Leung]

Hi Dink,

Sorry, I make typing mistake, Star Racing suggested valve size should be 29mm&24.5(in&out). The reason of upgrading the engine is that the performance of engine is going down and it is time for overhaul. By this overhaul, it would like to have something new and more power on it as I have this bike already 5 year for daily drive. I feel a bit boring. Two years before, it was installed the dyno jet kit 1 on it but it didn’t get better because valve is leak when it reach high rpm. All the upgrade items list from above was told by a guy from ebay and he said it is good enough for daily with top power. If it is too much, what are the best upgrade items for daily drive but with good power?

Addy

[Dink]

Addy try the bigbore 1260 with dialled stock cams and rejetting to suit, if that is not enough for you then bolt in your "hot" cams , maybe then try 38mm flatslides of a GSXR.
Dink

[skip]

star racing did work on my motor plus i have bought many parts through them. they do very good work but are not cheap. I have also done work with c&wperformance (Carl and Russ Nyburg) They did my head and were much more reasonably priced.

[Anonymous]

The cheapest way for you I think is to go with 28,5 mm AP Intake and 24mm AP Exhaust valves. You do a seat-job to fit the bigger valves but you dont need to replace them. BTW, they last very long and the job to put in 16 new valveseats costs a lot. New guides and a small porting job to fit the "new" seats and adjusting the rubber manifolds to the carbs will give you a engine with strong mid and upper torque. With the stock cams you should achieve about 135 Bhp maybe a little more and a maximum torque at the wheel around 115Nm. Be careful even on second gear
A fiend of mine just rebuilt his with the following: 1135cc, Stage2 ported head, 28,5mm Intake, 23(stock) exhaust with seat-job. Cammotion G21 cams(yes, recommended for the GSX-R1100), Mikuni Smoothbores33mm and my old V&H Supersport 4-1. He must be careful even on second gear not to see the sky :P Imagine that but with your 1260cc kit....I rest my case. Ohh BTW His engine has very good rideability in slow traffic even though he uses the 33carbs wich are known not to be smooth in character...GOOD LUCK

[Addy Leung]

Hi Everybody,

Thank vrery much for all kind & valuable advice.

It would like to ask two more question. 1/ it is about the rocker arms.
I remenber someone said the best stock rocket arms are from GS1150 and they also fit to GS1100.
If yes, what is that good and what is the benefit?

My local workshop owner told me if I go to 1260cc, it will properly get over heat during summer time 36degree C even using the Wiseco big block and work with a big oil cooler.
Will that happen?

Addy Leung

[Dink]

Yes Addy you should fit an oil cooler if you go big bore particularly in the climate you are in, as to the rocker arms I dont know for certain , but think that what you were told would be right.
Dink

[Anonymous]

Addy!

Go with the 1150 84-87 oilcooler and replace your oilfilter cap with one from the same as 1150. Go to your local hardware store and buy 2 longer banjo-bolts for the hoses wich are to be mounted on each side of the oilfilter, simply bolt on the lot and youre homefree. Remember the cap has to be replaced because otherwise you wont get any oilpressure. But honestly, why not go for bigger pistons? In Sweden, at one of the biggest tuning-shops named "Moto-Speed", they put in up to 1327cc, JE Pistons, in Stock cylinderblock. And the price of the pistons and sleeves are practically the same. Just a thought.

[biker66]

You said you were new to this, so I thought I'd make sure you don't forget that you have to machine the upper engine block for the bigger sleeves !
Easily forgotten in the excitement of the moment...

[Addy Leung]

big bore the bottom case?

Hi GS Rider,

When I checking parts in ebay, I found a bottom case (the part under the cylinder block) of an GS 1100 and it said it was already big bore for 1260cc upgrade. (http://cgi.ebay.com/ebaymotors/ws/eB...tem=2412062534 )

I wonder do it really to big bore the bottom case? In Wiseco web site, they said their big bore kit(including cylinder block with instaaled sleeves, 4x 1260cc pistons & pins and gaskets ) is ready to install and do not mention any thing about the bottom case.

Who is true?

Thanks for information from chrille_08.

Addy Leung

[skip]

I am 99% sure that 1229 is the largest kit you can do without boring the case. I think 1260 needs to have the case bored wich is why I didn't do it. I did mine many years ago so I may be fuzzy on the details