Some of you may recall my earlier posts about the poor MPG I was getting on my
1275 with a Dellorto DHLA 40.
Well, after trying to swap out my main jets, and also my pump jets, here's what
I found:
The original installed mains were marked as .135 (the recommended size for a
1275 is .140)
The original pump jets were .145.
I then tried new pump jets .140, and new mains .145 to see what would happen.
The engine was less responsive, but still ran well, and the gas mileage did
increase. This kind of made me wonder why the improvement on mileage with a
supposedly 'bigger' main jet.
I then thought I switch back to the larger pump jet, to see if that would
improve the engine response. For the heck of it, I thought I'd compare the 145
main jets to the 'original' DPO's 135's that I had, and guess what??, the holes
in the 135's were noticeably larger than the new 145's, and 140's that I had.
It
appears that the 135's were 'drilled' out to about 155/160. This could explain
why I was getting such poor MPG.
Moral of this story: Don't assume that factory markings are 'valid', or, why
'buy' larger carb jets when you can just 'drill them out';-)
- Bryan
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