Main jet size on 1135 engine

[John Kat]

My 1100 Katana runs with an 1135 engine inside.
The BS 36's carburation is spot on except at WOT.
I have to "nurse" the throttle around WOT to get more power.
I'm running with the complete OEM air filter setup, new carb boots and 120 main jets as per the OEM spec.
The exhaust is the OEM Katana exhaust.
I noticed that in some places the spec for the main jet is 120, 122.5?
I suppose this means that two carbs get a 120 jet and the others the 122.5?
Which ones get which?
Could this be the issue?

[posplayr]

My 1100 Katana runs with an 1135 engine inside.
The BS 36's carburation is spot on except at WOT.
I have to "nurse" the throttle around WOT to get more power.
I'm running with the complete OEM air filter setup, new carb boots and 120 main jets as per the OEM spec.
The exhaust is the OEM Katana exhaust.
I noticed that in some places the spec for the main jet is 120, 122.5?
I suppose this means that two carbs get a 120 jet and the others the 122.5?
Which ones get which?
Could this be the issue?

It sounds like you should be setup pretty close to a stock 1150 (or the 84-85 GSX1100 in Europe.) The 122.5's would be on the two inner cylinders as they run hotter. Other than a little less lift on the cams and a 1mm smaller intake valve you are pretty much at where the stock 1150 is.


Are you sure you do not have an ignition problem? Also even with a stock bore on my 83 GS1100 (but pods,pipe and cams) I would run out of gas due to petcock flow limitations (sustained high speed in 4th or 5th gear). I went to a pingle and problems solved.

The difference between 120 vs. 122 would be hard for you to tell at WOT unless you had an O2 sensor or were an expert reading a plug

[Steve]

I noticed that in some places the spec for the main jet is 120, 122.5?
I suppose this means that two carbs get a 120 jet and the others the 122.5?
Which ones get which?

Yes, the outer carbs get the 120s, the inner ones get the 122.5s.

.

[John Kat]

It sounds like you should be setup pretty close to a stock 1150 (or the 84-85 GSX1100 in Europe.) The 122.5's would be on the two inner cylinders as they run hotter. Other than a little less lift on the cams and a 1mm smaller intake valve you are pretty much at where the stock 1150 is.

Are you sure you do not have an ignition problem? Also even with a stock bore on my 83 GS1100 (but pods,pipe and cams) I would run out of gas due to petcock flow limitations (sustained high speed in 4th or 5th gear). I went to a pingle and problems solved.

The difference between 120 vs. 122 would be hard for you to tell at WOT unless you had an O2 sensor or were an expert reading a plug

You are right, it feels like fuel starvation!
The ignition seems OK and the spark plugs are new.
I did the tests in 4th and 5th gear at well over 100 mph
I'm not sure I understood the differences you are mentionning about the smaller intake valve between the different bikes?
Did the 1150 come in different versions?
Many thanks for the input

[posplayr]

You are right, it feels like fuel starvation!
The ignition seems OK and the spark plugs are new.
I did the tests in 4th and 5th gear at well over 100 mph
I'm not sure I understood the differences you are mentionning about the smaller intake valve between the different bikes?
Did the 1150 come in different versions?
Many thanks for the input

I'm assuming your 1100 kat has a stock head which came with 27mm intakes, the 1150 came with 28mm intakes. The 1100 Kat also had close to the same valve lift as the 1150. A ported head can significantly improve the flow.

[John Kat]

In fact my engine is a true 1135
According to the engine identification number it should originate from a GSX 1100 EFF from 1985?
I'm eager to test it again with the proper fuel flow!

[posplayr]

In fact my engine is a true 1135
According to the engine identification number it should originate from a GSX 1100 EFF from 1985?
I'm eager to test it again with the proper fuel flow!

Humm.......... I assumed you had an over bore kit. The head appears to be from 1100 which would probably be 82-83 head with 27mm valves. This must be some type of European version as the 83 manual for the SD Kat is not 1135 cc but the same 1074 cc as all the other 1100e's

[hillsy]

In fact my engine is a true 1135
According to the engine identification number it should originate from a GSX 1100 EFF from 1985?
I'm eager to test it again with the proper fuel flow!

If the motor is the one in the picture you posted above, that is not an EF 1135 motor (well, the head certainly isn't).

As for the jetting, stock mains for the EF are 120/122.5 as stated by the others.

Are you running a fuel filter or anything else that might impede fuel flow? This could be an issue if the problem is only at high RPM / WOT.

[chef1366]

What does the front of the block say?
That is not an 1150 head as stated.

[John Kat]

If the motor is the one in the picture you posted above, that is not an EF 1135 motor (well, the head certainly isn't).

As for the jetting, stock mains for the EF are 120/122.5 as stated by the others.

Are you running a fuel filter or anything else that might impede fuel flow? This could be an issue if the problem is only at high RPM / WOT.

You guys are making me doubt about my engine
As I bought the bike from a guy who used to do drag racing, I suppose every combination is possible...
I guess the engine has been prepped one way or the other?
When I rode the bike two days ago, I was amazed at how easily the bike revved when you blip the throttle to engage a lower gear?
Not at all like my other GS's...
With respect to fuel starvation, yes there is an inline fuel filter.
I'm concerned about running without one but at least I could easily replace it and try again

[John Kat]

What does the front of the block say?
That is not an 1150 head as stated.

The block is stamped 1135.
I suppose the head is from a GS 1100?
Does that give me more CR?

[posplayr]

The block is stamped 1135.
I suppose the head is from a GS 1100?
Does that give me more CR?

If someone was smart enough to swap out the 1074 block for a 1135 block they probably did other things to the engine as well. You could have an 1150 crank in there with a set of stock 1135 pistons (20mm pins v.s. 18mm for 1100) that came with the block. Given all that it would not be a big surprise if there was some head work done including putting 28mm 1150 valve into that head if all that were the case then they probably threw the 1150 cams in as well.

Have you had the valve cover off to measure the lobes or see if there is a cam gear? The 1150's were electronic ignition so there was no cam gear. All of the ED/ESD bikes had gears on the cams.

[John Kat]

Have you had the valve cover off to measure the lobes or see if there is a cam gear? The 1150's were electronic ignition so there was no cam gear. All of the ED/ESD bikes had gears on the cams.

No I haven't opened the valve cover yet.
I thought all GS's post 1980 had electronic ignition?
Where are the cam gears supposed to be?
Sorry for the ignorance on the 16v bikes...

[TeamDar]

Tach drive gear cut onto the exhaust cam.

[chef1366]

Yes, he meant electronic tachometer.