Reinhoud Posted June 8, 2020 Share Posted June 8, 2020 9 hours ago, smithy09 said: When I say we retarded the ignition, this was compared to the massive advance we had pre twin plug head. You cannot say "Don't" to apply across the board. All my timing mods were done on the dyno with back to back runs. Advancing the timing with a single plug head and around 11.5:1 compression made a massive difference. We gained 10-15 hp, might have even been more. However the heat generated must have been substantial and like you say, the chance of detonation is also there. When we went to twin plug, the timing was dialed right back, probably to around standard timing, yes. I have no experience with turbo'd engines but I guess it is just like having a very high compression engine, and the twin plug set up will help a lot. The advancing you mention, how many degrees are you talking about? Isn't 37 degrees already a lot? Quote Link to comment
smithy09 Posted June 8, 2020 Share Posted June 8, 2020 (edited) 19 minutes ago, Reinhoud said: The advancing you mention, how many degrees are you talking about? Isn't 37 degrees already a lot? I can't remember, and I'm away from home so I don't have my notes, but it was enough that we had to file extra length in the slots of the Dyna 2000. The HP gains were amazing. We did a run, advanced a bit, got a gain, advanced some more, another run, more gains, and so on until the hp stopped increasing. Found the dyno graph on my laptop! Advance was 40 degrees. These were with standard Wiseco 1100cc pistons, 10.5:1 before I went bigger. Unfortunately I never got a print out of the 150hp runs.. I will next time. Notice how the dip around 5500 rpm is less pronounced with the twin plug head? got rid of it altogether with the big engine. Edited June 8, 2020 by smithy09 1 Quote Link to comment
Reinhoud Posted June 8, 2020 Share Posted June 8, 2020 1 hour ago, smithy09 said: I can't remember, and I'm away from home so I don't have my notes, but it was enough that we had to file extra length in the slots of the Dyna 2000. The HP gains were amazing. We did a run, advanced a bit, got a gain, advanced some more, another run, more gains, and so on until the hp stopped increasing. Found the dyno graph on my laptop! Advance was 40 degrees. These were with standard Wiseco 1100cc pistons, 10.5:1 before I went bigger. Unfortunately I never got a print out of the 150hp runs.. I will next time. Notice how the dip around 5500 rpm is less pronounced with the twin plug head? got rid of it altogether with the big engine. Nice! Was it still running properly in the lower rev range? Quote Link to comment
smithy09 Posted June 8, 2020 Share Posted June 8, 2020 2 hours ago, Reinhoud said: Nice! Was it still running properly in the lower rev range? Yes. It was all OK, but just had that dip in the middle. In real life on the track it was a little annoying as you would be hard over mid corner, just exiting the corner when you came out of that dip in power and got a big rush, which wasn't good for rear wheel grip! The twin plug arrangement lessened that considerably but it was still there. Once I went to the big bore though, it completely disappeared. I was dreading riding a 150hp GS1000 on the track, but actually it was much easier to ride than the small engine. All was good until the crank broke!! 1 Quote Link to comment
cnap504 Posted October 21, 2021 Share Posted October 21, 2021 How big can you bore a GS1100gk cylinder for reliable street use? They are 72mm from the factory Quote Link to comment
Gixer1460 Posted October 22, 2021 Share Posted October 22, 2021 Apparently - 1170cc / 75mm bore with stock liners. Or 1260cc / 78mm bore with different liners in a stock block - any larger has to go Gorilla style block + liners, then the sky's the limit! Anything with a OEM block should be ok with some extra oil cooling for street use - maybe not city use though! A few people have used Gorilla blocks on street bikes in the UK without drama's but these tend to be WELL cared for bikes, not a daily beater! Quote Link to comment
cnap504 Posted October 23, 2021 Share Posted October 23, 2021 Who supplies these pistons, the largest 1100gk overbore I found was 74mm 1135cc from Dynoman. Quote Link to comment
Gixer1460 Posted October 24, 2021 Share Posted October 24, 2021 12 hours ago, cnap504 said: Who supplies these pistons, the largest 1100gk overbore I found was 74mm 1135cc from Dynoman. Info from American Performance Engineering (APE) website. Quote Link to comment
kiwi Posted November 28, 2021 Share Posted November 28, 2021 (edited) On 10/23/2021 at 11:50 PM, cnap504 said: Who supplies these pistons, the largest 1100gk overbore I found was 74mm 1135cc from Dynoman. Largest overbore before resleeve in a 1100G is 75mm (MTC) but if used in a GS1000 with standard crank and rods is 1146cc Edited November 28, 2021 by kiwi Quote Link to comment
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