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I am looking for ways to improve the gas milage of my /2 conversion with an R75/5 engine in it. It has a 3.13 /2 rear drive and I run a 3.50 X 18 tire on the rear so the overall gearing is close to a stock /5 with 32.10 drive. It has the small gas tank and my range is 120 to 140 miles.

I have been reading up on dual plugging and realize that it is part of an entire package of changes needed for performance.

My thoughts are to raise compresion up to the 9.5 range and dual plug to reduce the need for premium gas. I do not have a stock alternator so I am useing a cam driven ignition system. I am looking at the Boyer as they now have a unit with a dual plug advance curve, and I have had good luck with thier products in the past.

Has anyone out there experianced better gas milage with a switch to twin plugs?

Any other comments.

I haven't heard much about improved gas mileage...I think it's mostly to allow for running lower grades or gas or poor grades of gas as well as for ease of starting.

It's also critical to control the timing. I think the ideal is to have the stock static timing point but have a full advance timing point about 5 degrees before the stock point.

Kurt in S.A.

Kurt in S.A. wrote:I haven't heard much about improved gas mileage...I think it's mostly to allow for running lower grades or gas or poor grades of gas as well as for ease of starting.

It's also critical to control the timing. I think the ideal is to have the stock static timing point but have a full advance timing point about 5 degrees before the stock point.

Kurt in S.A.

I just got done doing the dual plugging on my project. They came out real nice (not to toot my own horn). I tried with 10mm plugs, but since I'm not adding material to the plug boss, they didn't seem to feel like they'd hold much torque. I opted to go up to the standard 12mm and they feel much better.
I think fuel economy can be improved, because dual plugging requires more precise carb adjustment.
I'll have to wait and see. Of course I'm only hoping to get close to what I had before, since I'm using a 336 cam and 1000cc, 9.5+:1 pistonswith this overhall.
What alternator are you using? I'm using a crank mounted ignition on my Enduralast. As long as you can mount the rotor to the end of the crank a bracket can be fabbed up to mount the trigger unit.

I am useing an MZ Power Dynamo. The MZ includes a crank trigger self powered ignition, but I found it to be hard starting at times and had a poor idle, probably from low current at idle. I now use it as a back up.



It is shorter than the stock alternator which allows me clearance at the Earles forks. With the cover on there is less than a MM between the rotor and the front cover.



I am thinking that improved fuel economy will come from raised compresion, and the dual plugs will make it streetable.

I know no one likes to read his website, but Snowbum has a page on dual plugging. He does say, though, that it probably results in better mileage.

http://bmwmotorcycletech.info/dualplugging.htm

Kurt in S.A.

Kurt in S.A. wrote:I know no one likes to read his website, but Snowbum has a page on dual plugging. He does say, though, that it probably results in better mileage.

http://bmwmotorcycletech.info/dualplugging.htm

Kurt in S.A.

Yes I have read that, with my dark glasses on.

Garnet wrote:I am useing an MZ Power Dynamo. The MZ includes a crank trigger self powered ignition, but I found it to be hard starting at times and had a poor idle, probably from low current at idle. I now use it as a back up.

It is shorter than the stock alternator which allows me clearance at the Earles forks. With the cover on there is less than a MM between the rotor and the front cover.

I am thinking that improved fuel economy will come from raised compresion, and the dual plugs will make it streetable.

I've never seen one of those funky contraptions.
The increased compression will help. I think, from what I've been reading, the key is to get the advance curve right with out making compromises on the bottom end. That's why I think the adjustable curves on the Omega are the way to go. I'm not sure what you can do with a Boyer in that regard. Does it come with a modified curve for dual plugging?

" I'm not sure what you can do with a Boyer in that regard. Does it come with a modified curve for dual plugging?"

Yes, they have a unit for dual plugs. I will get an advance curve from them before I go ahead it.

I seems to me that worrying about top end timing retard on a street bike (even with dual plugs) is unnecessary. Now, if you spend a lot of time at WOT with dual plugs it may be worth while to look into it. Of course the only way to really know is a lot of time on a dyno that can load the engine at steady rpm...8500 or so while you find the sweet spot.

Garnet wrote:

Kurt in S.A. wrote:I know no one likes to read his website, but Snowbum has a page on dual plugging. He does say, though, that it probably results in better mileage.

http://bmwmotorcycletech.info/dualplugging.htm

Kurt in S.A.

Yes I have read that, with my dark glasses on.

Did it help?