gsx1100ef (1150) - advice on engine mods

[Ådne95]

Hi! 

I've got a 1984 gsx1100ef (1150) that's ready for some work, currently in the planning/budget stages of the project. First off, I am going to EFI convert it, but when it comes to engine upgrades I would appreciate some input from the experienced guys on here! 

1. At 115hp from a 1137cc I-4, I guess it doesn't flow record-breaking amounts of air. Am I right that just getting performance cams (and valve springs) is kinda worthless without getting bigger valves and porting as well? 
2. Any other low-hanging fruit performance-wise?  Increasing compression ratio for example? 
3. I've read that bigger cams requires hardwelded rockers, and that using oil pump gears from a '77-'82 gsx750 makes more oil pressure. Any other stuff that's smart to do with these engines? 
4. This might be a dumb question, but is there any way to shed weight off of these engines? I found somewhere that the gs1100 engine is about 90kg/195lbs and I guess the EF  engine is even heavier   Any specific components that could be put on a diet or changed for lighter ones? 

Kind regards, Ådne

[Dezza]

What is your chassis spec? About all you can do externally with the engine to reduce weight is change the sprocket cover to something more rudimentary and fit a 4 into 1 exhaust. With chassis mods there's a lot more you can do weight reduction wise; brakes, wheels, suspension, 530 chain conversion and so on, with the added bonus of ending up with a bike that doesn't want to kill you when you ride over an uneven road surface at speed .

[Arttu]

I think larger throttle bodies with freely flowing air filter and good exhaust should give some noticeable improvement on power. At least my 1074cc GSX1100E gained about 15hp back in days when I switched to EFI and replaced the exhaust with more freely flowing one. And that was with relatively small 34mm TBs and very basic DIY 4-1 exhaust.

Beyond that it starts to get more expensive or difficult, I think. Normal tricks are increasing displacement, upping the compression, porting the head, hotter cams and so on. As you know. All these tend to cost quite a lot or at least require some knowledge and skills for DIY work. I'm not aware of any special bottlenecks in this engine that could be easily improved for significant gains. Or well, cam timing is worth of checking and adjusting if needed. Factory tolerances seem to be pretty bad so you may get quite nice improvement just by setting them to nominal stock values.

I would guess that some mild performance cams would give noticeable improvement even without head porting. But it's very subjective question if that is worth of cost. If your cylinders and pistons are in less perfect shape some big bore pistons with higher compression would be quite obvious solution. They should give results no matter what other modifications you do.

I don't see any easy ways to reduce engine weight. Besides that sprocket cover and possibly some other similar parts. Most of the weight is in the crank, cases, head and other similar parts. In theory you can probably shave some material off from here and there without significant drawbacks but the weight saving will be very small, I think. Or you can spend a fortune for fancy lighter parts (mostly custom made) and get more noticeable reduction. But even then it will be a heavy boat anchor in the end

[Ådne95]

6 hours ago, Dezza said:

What is your chassis spec? About all you can do externally with the engine to reduce weight is change the sprocket cover to something more rudimentary and fit a 4 into 1 exhaust. With chassis mods there's a lot more you can do weight reduction wise; brakes, wheels, suspension, 530 chain conversion and so on, with the added bonus of ending up with a bike that doesn't want to kill you when you ride over an uneven road surface at speed .

I haven't decided on the chassis plans yet. I have two bikes - the EF and a 1981 gs1100.  Currently leaning towards putting the EF engine in the GS frame and making a cafe-ish/restomod build with modern forks/swing/brakes/etc.  In an ideal scenario I would restore/build both bikes, but looking realistically on time and money It's more than enough to build just one - at least for the time being 

Thanks for the input!

3 hours ago, Arttu said:

I think larger throttle bodies with freely flowing air filter and good exhaust should give some noticeable improvement on power. At least my 1074cc GSX1100E gained about 15hp back in days when I switched to EFI and replaced the exhaust with more freely flowing one. And that was with relatively small 34mm TBs and very basic DIY 4-1 exhaust.

Beyond that it starts to get more expensive or difficult, I think. Normal tricks are increasing displacement, upping the compression, porting the head, hotter cams and so on. As you know. All these tend to cost quite a lot or at least require some knowledge and skills for DIY work. I'm not aware of any special bottlenecks in this engine that could be easily improved for significant gains. Or well, cam timing is worth of checking and adjusting if needed. Factory tolerances seem to be pretty bad so you may get quite nice improvement just by setting them to nominal stock values.

I would guess that some mild performance cams would give noticeable improvement even without head porting. But it's very subjective question if that is worth of cost. If your cylinders and pistons are in less perfect shape some big bore pistons with higher compression would be quite obvious solution. They should give results no matter what other modifications you do.

I don't see any easy ways to reduce engine weight. Besides that sprocket cover and possibly some other similar parts. Most of the weight is in the crank, cases, head and other similar parts. In theory you can probably shave some material off from here and there without significant drawbacks but the weight saving will be very small, I think. Or you can spend a fortune for fancy lighter parts (mostly custom made) and get more noticeable reduction. But even then it will be a heavy boat anchor in the end

Thank you for the answer Arttu! I've read quite a few of your posts   

15 hp just from EFI and exhaust sounds promising.
After thinking some more about this, I think the plan has to be tearing down the engine first to see what needs replacing.  I worked part-time at an engine workshop during university so I hope I could do most of the work myself, or call in some favours from my old colleague there. When I worked there, we built a motorcycle engine adapter for their engine dyno, hoping I can to put that to use eventually  

Ok, thanks for the weight input, sounds quite like I expected, but had to ask   

[gsxwill]

On 10/4/2023 at 3:02 AM, Dezza said:

What is your chassis spec? About all you can do externally with the engine to reduce weight is change the sprocket cover to something more rudimentary and fit a 4 into 1 exhaust. With chassis mods there's a lot more you can do weight reduction wise; brakes, wheels, suspension, 530 chain conversion and so on, with the added bonus of ending up with a bike that doesn't want to kill you when you ride over an uneven road surface at speed .

It's not that it wants to kill you @Dezzait's just making sure you know who's in charge 

Though granted the whole bike twitching just by touching white lines does make me rethink my life choices sometimes 

[Duckndive]

Given your location "Norway" your bike is most likely fitted with the "restricted" lower power cams "as were most European models" 

so a simple upgrade would be a pair of full power stock cams or "D" marked cams as they are often referred to 

 

[Ådne95]

4 hours ago, Duckndive said:

Given your location "Norway" your bike is most likely fitted with the "restricted" lower power cams "as were most European models" 

so a simple upgrade would be a pair of full power stock cams or "D" marked cams as they are often referred to 

 

Thanks a lot, good to know! 

[Ådne95]

I've got another question, regarding cams;

I see Web cams are about £845, Kent JR3 cams are £325 - how is the quality of the Kent cams? any explanation for the price gap?  

From reading various threads, the Web cams with .340" (or maybe .348") lift should be fine for what I want, the JR3 cams state 5.57mm lift, which equals 0.219"... I assume this is measured at "different ends" of the rocker ratio??? I cannot seem to find the rocker ratio anywhere - how do these cams compare performance wise? 

[Gixer1460]

Web cams are likely ground on fresh cast billets, Kents more than likely regrinds on old cams would explain cost difference. I'm guessing the specs are noting different things as you suspect - Web = installed valve lift, Kent = measured lobe ht. from base circle ?

[Ådne95]

35 minutes ago, Gixer1460 said:

Web cams are likely ground on fresh cast billets, Kents more than likely regrinds on old cams would explain cost difference. I'm guessing the specs are noting different things as you suspect - Web = installed valve lift, Kent = measured lobe ht. from base circle ?

Ah, of course - makes sense  Unless anyone here has input on the difference, I'll just have to get going on dismantling the engine this winter so that I can measure rocker ratio. 
 

Currently on sick leave with a screwed up foot after a wreck, this means a lot of time sitting in hospital beds and now sofa at home... so I've done some planning and made a budget for parts prices I need/want - not really sure how smart that was, I think ignorance is bliss when it comes to project costs  

Edited October 14, 2023 by Ådne95
spelling

[Arttu]

Rocker ratio is 1.6:1 according my notes...

[Ådne95]

10 minutes ago, Arttu said:

Rocker ratio is 1.6:1 according my notes...

Thanks a lot Arttu!   Kent JP3 cams have an equivalent of .351" lift then   you don't happen to have any experience with those cams ? 

 

[Arttu]

40 minutes ago, Ådne95 said:

Thanks a lot Arttu!   Kent JP3 cams have an equivalent of .351" lift then   you don't happen to have any experience with those cams ? 

 

Unfortunately no. I have been using only stock cams except one unlucky experiment with Web cams