!910 Engine Boost?

[Michael.Voice]

Perhaps you could try some avgas in it. Aviation fuel has a much higher octane rating and as such, tends to run a little cooler from my experience and will give you plenty of extra power during running. I had to use avgas back in the days of the change-over in New Zealand to unleaded... which as we all know... is ****. Without lead in your fuel you get poor combustion, waste more petrol over the same distance, and wreck your valve seats which will over heat and burn the edges. If I could run avgas in my early bikes all the time, I would.

Oh yeah, you should be able to pick up a bit of avgas from any local airfield, if you know someone there.

Good luck.

Michael Voice
10556

[wyatt emp]

That is correct.

[c.o.]

Great to hear! I assume now that you can make it to the top of your drive-way?

[wyatt emp]

I did find that I would loose compression while under way and that by pushing down on the valve and spring a couple of times would fix the problem. Assuming a stronger spring might do the trick, I replaced it with one and gained the power I need. Atmospheric conditions or just a weak spring, who knows? Inertesting thoe......

[Tommo]

Rob I could see this coming and was just willing you not to ask that question.
In short it just complicates the issue being discussed.
Set the tension for the best performance at the altitude you most ride the bike at and be prepared to suffer the consequences when you ride at significantly different altitudes.

[rwm]

Acton varies from 2500 to 4000 feet.

what dose that do to an atmospheric valve?

[Chris Haynes]

Acton varies from 2500 to 4000 feet.

[rwm]

how high above sea level is acton ca?

[Tommo]

I put about a pint of Av gas to every gallon of 91 grade gas I use here in NZ but this is done as a lead addittive rather than for any performance gain.
Someone over there should be able to give you better advice on this subject but with valve recession in mind I'd be looking to try and get some lead into the fuel to help with valve seat life.

[wyatt emp]

The guy that rebuilt it knew what he was doing so probably where it should be. He even replaced the babit bearing with bronze. I am running regular unleaded gas in it. Would it run better on premium or with an octain boost additive?

[Tommo]

Sorry Wyatt I didn't answer you question.
It could be a carb problem but it could also be a spring tension problem as I outlined in the above reply.
Too little tension and the valve doesn't shut quick enough and some of the charge is blown back through the carb.

[Tommo]

When it comes to setting AIV spring tension there is a very fine line between too little and too much.
Too much and the inlet valve is slow opening and therefore doesn't get a full charge into the cylinder and with too little tension the valve is slow closing and some of the charge gets blown back out the inlet valve.
One's as bad as the other and there's no easy answer as how to achieve that magical correct tension as each and every engine is slightly different and therefore requires a setting that suits that particular engine.
Your valves and seats must also be in perfect condition and the inlet valve seat should be as narrow as possible. Wide seats hinder the flow of the incoming gases and result in a considerable drop in power.
Near enough in this situation is not good enough and it's a bit like tuning a piano, to be right it's got to be spot on.

[wyatt emp]

Tommo: There does appear to be a possible air leek in the carb around the throttle valve as when I turn it out when the motor is running some fuel will spurt out. Is this a possible problem?

[wyatt emp]

Did you know him? Looks like it was some time ago, then I saw a video of him being arrested by police and then a latter one where he was in a wheelchair???? Anyway not to get off topic I know we were joking about AV fuel but what about some kind of additive like octain booster?

[c.o.]

Jeff was famous for blasting around Seattle on that '12. He believed in riding them that's for sure!