Have some conflicting information on what the gap should be. I run the QS100, QS150, and standard 140. What are you guys doin...

I am running and always have run on my 50i,70i,75 twin spark,85 twin,and my 106 twin= NGK cm-6 at a gap of 25 thousand's

Interesting! Not only about the gap, but that you are the only reply, Thanks. I will presume that is with the stock ignition. The reason for asking is that I was always told that when I get the plugs, they are gapped for the 3W. They are not .025 though, more like .017 What might be the running differences between the two gaps? Take care_bob

I'm not sure about the differences on the 2 running characteristics,I always check my gaps though.Some need to be changed some don't,It's just like a car they say they are already gapped but it's just a little extra insurance for me to double check ever time I replace a plug.
I don't think the .008 difference is really an issue,I have a good spark at .025 so I will continue to run them there.Hope that helps. Terry

fryfly,

How is the performance on the 3W-85? I'm getting 6000 on a 3W 26x10 and it kind of seams to be lugging that prop slightly on the up lines. I'm curious if my engine is performing where it should be. Which carburetor does your engine have, Walbro or Tillitson?

Also which produces the most power, 3W-75TS single or the 85 twin?

Thanks,

the 85 twin runs better on a 26x8 3W prop,the tips with this prop would break the sound barrier and would absolutely rip the 27 pound laser it was in,My 75 twin spark isn't broken in yet (only one tank of fuel through it) but seems to have more power than the 85 twin. From flying both engines I think I will like the 75 twin spark better in the long run after it is broken in.
The 75 twin spark is pushing 8 horse at less weight !!!! than my 70i at 6.5 horse.With an extra couple of cc's and one more plug this lighter engine is putting out and extra 1 1/2 horse compared to the 70i It's worth the weight savings over the 85 twin.
All my engines have the Tillotson carbs installed, and all have run super for me. I believe the only advantage the 85 twin has over the 75 twin spark is the smoothness of the twin versus the single.

Believe it or not I picked up a tip on gapping plugs with a #11 exacto blade. It works everytime for me with "0" issues. I have been doing this for a long time on all the gassers I have had. I have not miked an exacto #11 but it does work..Walt

I heard the same thing. They mic out at .020 Cool!

I use this piece of steel that has an .018" stamped on it.
When I check it with a micrometer......it measures .018".
What a coincidence......

Bob, 3W are a very efficient 2C engines, well ported, well made, well field proved.PERIOD. About spark plugs, please don't try to reinvent the wheel NGK are the best spark plugs availables at reasonable price. I`m also in the world of go-cart racing and outboard racing, and every engine is a particular requirements. For example, there are by 34$ special spark plug (NGK) for carting racing, but also the 4$ plug will work but only the first two or three laps, and after that the heat start to build up and oil deposits too, engine start loosing power and every laps time goes up, but hey run at 13000RPMS wow is like a glow plug. In our case a 3W is a torque engine schneuler and boost ported like modern bikes and race outboard but always is but, you should have your best power range(torque) between 6500 and 7500RPMS engine can goes more up but is really a waste if you dont need that(stock engine not TOC engines) also 3W engines have a relative high compression, and as air fuel mix is more dense inside combustion chamber, more difficult for the spark to JUMP the electrode, but for this reason the have a well and strong ignition which deliver a strong pulse.The gap that our friends recommend .018 to .025 is OK Remember this engines use a lower oil ratio than conventional two cycles engines so if you add this with a well ported engine and good compression you will find a much better and easy to explode mixture and at the right spark time. What you have to be carefully with the gap is the oil quality are you using and of course the right ratio recommended. Be worried about your engine idles OK instead to reach full WOT rpms, small gaps are much easyest to cause problems at idling specially with high oil ratios and junk oils.

Hope this helps and please guys correct me if I`m wrong

Not trying to re-invent anything, just sort through some information to do the right thing. I use Lawnboy ashless for break in, and 3W oil after that. Thanks again and take care_bob

Bob, sorry if I offend you but maybe my leak of English makes you could misunderstand me when said "reinvent the wheel" it was just an expression. About the spark plug, go with NGK MC6, and recommended gap. For oil, may ask you were did you get your engine? the should give you some information. Boby at Cactus gave me plenty information at first time and he said to use Honda HP2 oil in a ratio 50:1 . You can also use the ZENOAH oil which is a good one too. For break in you can use a lower ratio like 48:1, I`ll on mine and see how much fouling after first tank. Also I have a bunch of Klotz blend which I use on my racing boat engine and this also should perform well. Very important Bob is the type of fuel you are going to use. Remember as higher the octanes it burns slower. High octane is more suitable for high compression engines and with timing advance sistems. Our engine falls in this category. If you use lower octane, you could have preignition problems and also het problems. Use premium unleaded. Dont store you prepared mix too long, try to use mix not olders than a month.For this reason I`ll suggest to have a graduated cup so you can prepare the mix in small amounts and if very few remains, will not be a problem. :thumbup:

I'm not offended. Just wanted you to understand, that's all. The Lawnboy is what was recommended from AI. I guess the octane thing has always been another gray area for me. For that reason I use the middle of the road Texaco and it seems to be doing OK so far. My 100 was really clean inside after 5 gallons of break in at 50:1 Thanks and take care_bob