Quote:
Originally Posted by DannoXYZ
You're close to maximum-timing anyway. More won't give you much even if you bump up octane to 117. Full exhaust will give you +22% +6bhp. About as fast as 300. Even better to increase compression and displacement. Way, way more gains than anything else. People have gotten double factory power this way.
Here's chart of bone-stock 250 with snorkel removed. It's got way, way too much fuel anyway. Your carbs are most likely dirty and clogged. Need complete carb disassembly and restoration... And get a wideband, reading tea-leaves gets expensive with buying new plugs for each run.
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I guess I should have said I have a Pre-gen. It’s a 95, but I think the timing is already advanced much mote than the 08+ ninjas.
I worked hard before to get the jetting just right 3 years ago when I first put the sidecar on. The K&N filter that covers both carbs did great for flow and evening out the air a bit. I initially had a 118 main jet when I put emgo shorty mufflers on my exhaust, but they did nothing for actual sound deadening or back pressure and were brutally loud. After a couple weeks I put a 2-1 exhaust and a gsxr 1000 can I had lying around, it reduced a lot of noise, and gave me some back pressure, and I brought the main down to 115 since it was running a bit rich.
My carbs are squeaky clean, I ride this thing a ton, and a lot of fresh fuel goes through them.
You’re right about the power increase from the exhaust and intake. It had significant gains at first. I’m hoping to take this to bonneville this fall to set the sidecar 250cc record, and was hoping I could find some who had tried bumping the timing more.
I put in my 118 jets this afternoon and took it on the freeway. It does go faster from before by about 2mph, but I don’t know if the side wind was aiding me or hindering me. And again, I fixed a vacuum leak so it may have been what was robbing me of power. I still can’t get any color at the end of my porcelain, and it looks as if it’s still lean. I haven’t cut them open yet though. I didn’t think advancing the timing would call for that much more fuel, but I’ll have to order even bigger jets until I can see it in the plug. I do have a wideband O2 sensor on my turbo nitrous Subaru powered vw bug, I’ll see how hard it’ll be to swap that over to the bike, might not be worth it.