Tohatsu S & 18 L carb timing

[Sea Rider]

You should have 180? flat butterfly at the end of the high hill cam when timming advance reaches 25? timing, though same for the L model, but 2 stroke 18 L models are being factory delivered with butterfly matching 180? at about 22? timing, they even are greasing high hill of cam for roller to slide better once at high hill cam end, smoothing cam over actuation issues.

Thought this adjustment was a timing issue found in just one L engine, but not on 4, so they are being factory delivered as stated. If you like going at constant wot, with use will begin to wear white roller pin and roller arm specially if working dry or not well lubed. Before adjusting factory same as the S model. Would like to know.

What implications for better or worst performance does this early 180? carb at 22? gives compared to same 180? at 25? timing ?

Happy Boating

 

[pvanv]

Re: Tohatsu S & 18 L carb timing

What does your experience tell you? What do the specs for the new motors say? 3 degrees retard may be tuning for lower-octane fuels. Japan has good gas... better than most of the rest of the world, so maybe they are slightly de-tuning those motors for use in Peru and similar areas. No reason why you can't set a motor to 25 degrees at WOT and test it, to see if it impacts performance. Probably minimal effect, since it's only 3 degrees. Of course, more conservative timing tends to add longevity to the motor -- in any application, becuase it doesn't run quite as hard, reduces the occurrence of pre-ignition pinging, and may reduce intake spitting. OTOH, if the advance cam is different than the older units (that went to 25 at WOT), advancing the timing at WOT may advance it too much for a smooth idle. A few tests will reveal your answers. Since we don't sell carbed 2-strokes in the US any more, there is no way for us to duplicate your conditions here.

 

[Sea Rider]

Re: Tohatsu S & 18 L carb timing

Paul, this issue is just found in new 18 L, new 18 S comes factory adjusted as usual, that is 180? at 25?. 18 L comes 180? to 22?, but cam's high hill will stop at 25? but with butterfly being already at 180?, the only issue that slight worries me is the over actuation of the cam against related plastic parts.

In the long run, running at near or full wot will wear roller plastic pin, roller arm at base (where it pivots) and butterfly side bushings if run dry.. All other throttle links settings remains same as S model.

Anyway, will move carb setting to match S model setting, place a TT and check max rpm at wot, probably will need to go a tad less pitch as this horse will be placed on a wider and heavier rib to obtain near 5800 rpm at wot with just me.

Happy Boating