The first engine I ever rebuilt was from a snowmobile I had back in the '70's. An older neighbour, who was a mechanic, said I could use his shop and he would give me a hand. I was a kid and wanted it fixed in 20 minutes and started rushing at it. He grabbed my hand, gave me a "Whoa There" and said, "The first lesson here is that there is 10% more horsepower in a properly assembled engine and it's the cheapest power gain you can get, slow down, do it right".A decent WERA legal superstock first gen SV should be getting 72-75 rwhp. That is a totally stock motor with a valve job and very careful assembly with timed stock cams, thinner head gasket, stock airbox and rejetted stock carbs and an M4 exhaust. My last stock motored racebike made slightly less than that as I had not slotted the cam sprockets and was running a Micron exhaust.
Kept in mind this is an experiment using a single vintage throttle body similar to ones used on some early nascarLooking at that dyno chart and ignoring any differences between dynos ( they can be significant), let's focus on Air:fuel ratio.
Was the throttle 100% wide open by 4,000 RPM? If not we have a transient and part throttle issues. If it was wide open, we can focus on that.
At 4,000 it's the same as from 7,000 up to the red line and that's a bit rich all the way. His chart has a dotted target line at 13:1 which is close enough for government work. In theory 12.5: 1 is ideal but the curve is pretty flat around there, so go a touch leaner to 13:1 and it will be close enough to spot on. The GS is quite a bit rich all the way up the rev range, so I would lean out the whole thing slightly before tweaking the 4-7 region. Watch the torque curve and it should rise across the whole curve. When that's right, start looking at that lower rev range.
Not too shabby for a first dyno trip.
No it looks like brass, unfortunately Getting another one is not an option, I have been collecting these throttle bodies for 20 years and never seen one this size before. Thanks for your thoughtsIsn't the butterfly aluminum? If so, you should source a new one that seals off completely.
Thanks, I feel the same, the net has info about putting JB weld in the bore but I just don't trust the idea. Making one is beyond me it's not just a plate.IF it really is brass, solder should stick fine. If anodized aluminum, you will have to make a new one. You could try JB Weld build-up, but I wouldn't trust it on the intake.
Today I soldered around the throttle plate and filed it to shape it now snaps closed to about a 3 deg angle. No sticking and although I can see light around most of it when held up to the sun I am happy with the fit.IF it really is brass, solder should stick fine. If anodized aluminum, you will have to make a new one. You could try JB Weld build-up, but I wouldn't trust it on the intake.
The cct only comes on with ignition and I was going to keep the vacuum petcock which will stop fuel flow if the engine cuts out with ignition on. In a accident it might cook the pump running dry, but if I have had an accident I don't think I will care.I like electric fuel pumps, dislike vacuum or "pulse" pumps. Electric pumps need care in wiring to stop them in event of crash. Probably using oil pressure with bypass to start circuit should work. More complex includes bank angle sensors. For a cafe, at minimum take care that key off kills power.