Tomos A35 gap setting -- 0.5 or 0.8 mm?

What started as an innocent 'skill-testing' question on the general discussion board has turned into a confusing controversy: I said I would give some free movie coupons to the first person who correctly answered the question "What is the manufacturer-specified spark plug gap setting for the A35 engine?"

The answer I expected was 0.5mm (~0.02in). If you go to the TomosUSA (or Canada) web site, go to the 'showroom' ( and then click on the maintenance schedule for any A35 bike you will see that the spark plug gap should be set at 0.5mm. On the other hand, if you go to the A35 manual ( you will find the gap should be set at 0.8mm. This seems like quite a significant difference to me.

I am more likely to believe the A35 manual, although I'm guessing that many people may have made the 'mistake' that I made and looked at the web site to find the gap setting. I actually just changed my spark plug and used 0.5mm as my gap.

So, I'm curious, what do people here use for gap setting, and is 0.5 vs. 0.8 (a 1.6-fold difference) really relevant?


Re: Tomos A35 gap setting -- 0.5 or 0.8 mm?

gaps are recommended for a particular year / engine / bike .. things like changes in oil mix ratio, commonly available fuel quality or octane rating, and ignition component alterations, etc., might then suggest to the engineers that some particular gap is more suitable than another, older recommendation.

And an old bike is likely to have a different ideal gap than what was suggested in the manual for the new bike .. same goes for plug heat range, ignition timing, etc.

So, imo, there's no "correct" gap carved in stone somewhere .. if symptoms suggest the spark plug gap might not be ideal, experiment with it. Or, if you have a dynomometer and are tuning an engine, a plug-gap change might make better power somewhere...

Re: Tomos A35 gap setting -- 0.5 or 0.8 mm?

Don Pflueger /

a larger gap is better for low end performance while a smaller gap is better for top end performance. keep in mind that tomos builds different versions of the same engine for many applications. for example, the sprint may use the wider gap because it is designed to be a slower bike while an lx may use the smaller gap because it is designed to be a "fast" bike. but its still the same engine.

sorta like the differences in a chevy 305 used in a car or truck. same engine, but little differences in some of it components to make it work for that specific application.

i'd go with thesmaller gap myself. check since thats their home site, not tomos usa.

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