Author Topic: Larger main jet...  (Read 1936 times)

Offline Mikep328

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Larger main jet...
« on: November 03, 2024, 08:31:08 AM »
I would like to try the next size larger main jet from the OEM 75s.  DSS does not seem to carry anything other than the 75.  Are larger sizes available nowadays anywhere?

I've been thinking about that for a while re ethanol blend fuels and since I have the carbs off at the moment for a different reason, it would be a good time to change them/perform the experiment!
Mine:
1976 CB400F
1973 Norton 850 Commando
2015 BMW R9T
2017 BMW R1200RS
2021 Moto Guzzi V7 Special
Wife's:
2015 Ducati Diavel
2019 Honda Africa Twin
2019 Honda NCT750

Offline ozzybud

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Re: Larger main jet...
« Reply #1 on: November 04, 2024, 01:16:19 AM »
CMSNL has OEM 80's.
Why do you want to go larger?  Pods?
1976 Z50 PARAKEET YELLOW
1970 CT70 CANDY SAPPHIRE BLUE
1971 CT70H CANDY TOPAZ ORANGE
1972 CT70H CANDY EMERALD GREEN
1973 CL200 CANDY RIVERA BLUE
1973 CB350F FLAKE MATADOR RED
1974 CB350F GLORY BLUE BLACK
1975 CB360T LIGHT RUBY RED
1975 CB400F VARNISH BLUE
1975 CB550 FLAKE SUNRISE ORANGE
1976 CB750F CANDY ANTARES RED

Offline Mikep328

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Re: Larger main jet...
« Reply #2 on: November 04, 2024, 07:53:47 AM »
"CMSNL has OEM 80's."

Thanks!  I was thinking that ONE size larger would be correct to compensate for E10 fuel's reduced BTU output compared to E 0.  IOW, one size larger with E10 would make the same max power as the standard 75 on E 0.  From reading some Keihen info this morning, it sounds like a #78 would be one size larger.

OTOH, the bike runs great and, based on info here, I'm going to switch to E5 assuming it's readily available at stations in my area so I'm no longer looking to change main jets... at least for now! 
Mine:
1976 CB400F
1973 Norton 850 Commando
2015 BMW R9T
2017 BMW R1200RS
2021 Moto Guzzi V7 Special
Wife's:
2015 Ducati Diavel
2019 Honda Africa Twin
2019 Honda NCT750

Offline TrickyMicky

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Re: Larger main jet...
« Reply #3 on: November 04, 2024, 09:06:01 AM »
Just as a matter of interest, My 400 is bog standard, even running OE points, coils  etc.,  I use E5, Shell where possible, and so far no problems.  At the end of a ride I close the fuel tap a little way from home.  After ir's been stood for 2 or 3 weeks, I turn the fuel on, give it a few seconds to find its way to the carbs, then it's full choke, a whiff of throttle and it starts.  My main criteria is that the engine does not get started unless it's going to get ridden far enough for it to get hot.  I suffered many years ago with a CB750 that I used for my 3 mile each way journey to work.

Offline Mikep328

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Re: Larger main jet...
« Reply #4 on: November 04, 2024, 09:39:42 AM »
I also close the fuel tap but I don't have a good feel for where to do that.  There is a lot of traffic in the vicinity of our garage (about 3/4 mile from our house) and I don't want the bike to suddenly quit while dealing with it!  So most of the time I end up idling outside the garage with the fuel off until the engine quits.  Sometimes that takes what seems to be a rather long period of time! 
Mine:
1976 CB400F
1973 Norton 850 Commando
2015 BMW R9T
2017 BMW R1200RS
2021 Moto Guzzi V7 Special
Wife's:
2015 Ducati Diavel
2019 Honda Africa Twin
2019 Honda NCT750