Bonneville America Forums Forums Technical Forums Performance Mods Looking of some support

While tooling round Lake Champlain I stopped by a place called Go Slo Engineering in Fort Ann, NY. I have driven pasted this place hundreds of time during my weekly trips to Fishkill, NY for my 2 1/2 years of controls projects at IBM. Back to the point, I noticed they had a dynometer listed on their sign so I stopped to inquire. Turns out it is a sales and service shop for Harley/V-twins, customs and restoration. This place is not a dealership, they are about service. I asked about the name and was told it was from the founding owner, who was a fanatic about doing it right the first time. I spoke with Paul the present owner about scheduling a dyno run. I told Paul, I had change exhaust, removed the air box and re-jetted and was curious about the air/fuel numbers. I explained the seat of the pants tuning felt alright but what did my untrained butt know. He said if I had some patience he would try and squeeze me in. He said he didn't have time to set the room up like he would usually for his dyno runs.

We got some stead state readings at constant load:
RPM Air/Fuel Ratio
2000 12.6
2500 12.0
2700 12.2
3000 12.6
3500 12.8
3800 12.8
4000 12.6
4500 12.2
5000 12.2
He did a couple of full pulls, there weren't any flat spots but it showed running rich the whole range.
We set the mixtures screws for exactly 13.8 at about 2 turns by sniffing both side. Paul said his best guess would be to drop the mains to 142.5 from the 155s, remove the Thruxton needles and switch back to the stock needle with 1 shim. I thought I might be running rich even though the plugs looked OK, just slightly gray. I didn't think 12.2 was to bad on the rich side but it does explain where my mileage went, down to mid thirties from high forties.

Tomorrow morning I was going to try the much talked about seldom attempted needle and main jet change without removing the carbs or fuel tank. I know it shouldn't be that difficult, but for a fat fingered, near sited , software geek this could be a feat. Did I mention questionable coordination? Anyway I would like some supporting feed back before I attempt this death defying stunt. Thanks in advance for your support.

it is, in fact, not that bad IF you have already changed the carb screws to allen head. if not, I'd say, bite the bullet and remove them, rejet and install allens. Then next time will be easy. Doing it in situ with stock screws can also be done, but can be a real ball breaker
G

Interesting. I've always felt the same way about my SOTP carb tuning.
I'll have to check the place out, but probably won't have my bike. I stay at that Courtyard in Fishkill occasionally and sometimes have time to kill.

Go Slo isn't much to look at but the guys were cool to talk to.

I got to thinking last night. I have been told that is a dangerous situation for me, I could pull something! Any how, if my limited understanding of the all the carb information I have read is correct, changing the needles back to stock from Thruxton needles should help reduce the rich condition. If I am in error please correct me.

OK, I chickened out and pulled the gas tank and only changed the needles back to stock with one shim. I must be learning something cause it only took about an hour. I have a habit of losing things right under my nose. I'll have a test spin on the interstate later this morning after I check the carb balance.

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I have a habit of losing things right under my nose

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Me too. I learned to use an old tupperware bowl (the flatter, the better) to collect all the screws, bolts, etc.

If your bowl is empty when you are done, good job!!

actually 12.8 give or take isn't bad at all, 13 is about perfect. At 12s you won't hurt anything except you are not getting optimal performance and like you said your mileage will be slightly less.

I just did mains, pilots, and shims this morning. Don't see how you could do it first time without removing carbs. I did put in all allen heads with lockwashers so if I need to go back it's easy. Those factory carb screws are REALLY tight-I'm sure I would have mucked it up had I not removed the carbs.

I had to pull my carbs the first time the screws were just too tight to get out at the angle they are when installed. Might not be like that in all cases. That first time I replaced with allen head screws and only had to pull them 1 other time to change a pilot jet that was being stubborn. I think if you are just learning the carbs it is a good idea to pull them and get a good look so you are familiar with the placement of the different jets and float parts. And while you are at it could get rid of that hidden inline filter and replace it with one you can get at to change or clean.

I've had my carbs off completely 3 previous times. I changed the stock screws to Brent's allen head screws when I installed the Freak. I pulled the gas tank when I change the needles just to make it easier. If I had a pair of 90 degree needle nose pliers and one of them fancy 90 degree allen screw things I probably would have left the tank on and tried to change the main jets too, before heading to the NE rally. Changing back to stock needle with 1 shim didn't seem to hurt the performance any, but it sure helped my mileage, back to the low forties. If anyone has a suggest on a tool to handle the allen screws w/ washes that you can't seen when the carb are in place, I am all ears.

Sears has a ratcheting screwdriver. Used with a 3mm bit, it's perfect. I also have the offset ones.

Bought this many moons ago on Phils recommendation. It's a must have for bike work, can't beat the price. I had a Craftsman screwdriver/bit set and those bits fit this piece perfectly making even more versatile.

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Sears has a ratcheting screwdriver. Used with a 3mm bit, it's perfect. I also have the offset ones.

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