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 Post subject: F1 Jetting and Plug Fouling
PostPosted: Tue Jul 09, 2013 10:27 am 
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Joined: Fri Jul 05, 2013 6:51 pm
Posts: 30
Hi Gents,
I have been having an issue with my new F1 with the plugs fouling (black and sooty) at low speed runs around town, and thought I might ask a question about the jetting of my bike. It currently has 40mm dellortos with mess bell mouths with a Verlicci style pipe.

I have checked the rear carb and found the following

Main Jet 152
Pilot Jet 70
AB 265 atomiser
Needle K4 (clip on 2nd)
Slide 60/1
Pump Jet 50

I am assuming the front carb with be similar with a possible slight difference on the main but will check anyway nd will be checking compression and leak down.
I was expecting to have similar jetting the the special F1s but there are a few differences.
Any advice on where to go as a start? Bike seems to pull fine from down low and revs out fine .

Cheers


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 Post subject: Re: F1 Jetting and Plug Fouling
PostPosted: Tue Jul 09, 2013 8:49 pm 
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Joined: Thu Oct 14, 2010 11:23 am
Posts: 1151
Are your chokes still on/engaged? MikeV


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 Post subject: Re: F1 Jetting and Plug Fouling
PostPosted: Tue Jul 09, 2013 8:54 pm 
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Joined: Fri Jul 05, 2013 6:51 pm
Posts: 30
Hi Mike,
The carbs only have those float tickler things.

DJ


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 Post subject: Re: F1 Jetting and Plug Fouling
PostPosted: Tue Jul 09, 2013 9:56 pm 
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Joined: Thu Oct 14, 2010 7:30 am
Posts: 140
I would have a look at the float levels [17.5-18.5mm, carb inlet down,float tab resting on needle] and maybe drop the pilot down to a 65.
Be aware 40mm carbs on a 750 aren't really suited for around town type running and if you get a consistent idle you are among the very lucky few.


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 Post subject: Re: F1 Jetting and Plug Fouling
PostPosted: Tue Jul 09, 2013 11:27 pm 
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Joined: Fri Jul 05, 2013 6:51 pm
Posts: 30
Good point,
I have ordered some 65 pilots and k5 needles to see how that goes but in the end may try to find some 36's and an original exhaust , If I can find 36mm dellortos I assume I will just have to go up on the mains with the free flow exhaust?
I know bevel heaven sells new 36mm PHF dellortos they may be an option.


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 Post subject: Re: F1 Jetting and Plug Fouling
PostPosted: Wed Jul 10, 2013 11:08 am 
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Joined: Thu Oct 14, 2010 11:23 am
Posts: 1151
Hello DJ. I was not being flippant about the chokes; I have seen the problem before when the flip-up type are left up, or not turned correctly and are still part-way up.

If you check the front carb the main jet should be smaller than on the rear --- say 148 or 145. You could move the front main to the back and get a smaller jet for the front --- say 140 --- and give it a try. It may need even less; too-rich settings seems to have been a practice in the past.

40mm carbs are a bit much if the engine is not up-graded in other ways, but they can be made to work. And, changing to 36mm will also mean manifold changes!

MikeV


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 Post subject: Re: F1 Jetting and Plug Fouling
PostPosted: Wed Jul 10, 2013 12:11 pm 
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Joined: Fri Jul 05, 2013 6:51 pm
Posts: 30
Hi Mike,
100% appreciate the advice , my background is 2T Yamahas race and road so this is new for me I had never seen a float tickler before let alone a dellorto pumper carb :D.
The front carb is set the same as the rear so i believe there is a lot of room for improvement but going to the LS, SM, M settings for this one, unusually the pilots look like the number is scratched on them rather than stamped ??

I have ordered 65 pilots, K5 needles, and 148/155 mains .

cheers for the info about needing new inlets if I go to 36's , I might just collect some bits as they come up and sort out what I have.


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 Post subject: Re: F1 Jetting and Plug Fouling
PostPosted: Wed Jul 10, 2013 8:35 pm 
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Joined: Sun Nov 07, 2010 10:54 pm
Posts: 425
Location: Brisbane
Hello DJ,
From memory my 750 is 145 mains and 65 pilots, 70/ slides and K6 needles,,,, "from memory"!
I can take a carb off and confirm if you need.
It runs well over all throttle openings on 98 unleaded.
The old leaded fuel could use larger mains than unleaded from what I've seen.
(pumps disconnected)
Graeme


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 Post subject: Re: F1 Jetting and Plug Fouling
PostPosted: Wed Jul 10, 2013 11:01 pm 
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Joined: Fri Jul 05, 2013 6:51 pm
Posts: 30
Hi Graeme,
do you run 40mm carbs and a similar exhaust? It would be great to know a working setting if you could check for me. Much appreciated. And no hesitation problems with the pumps disconnected?
I was surprised to see that inside the inlets were absolutely spotless, I had thought there would be staining from years of fuel.


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 Post subject: Re: F1 Jetting and Plug Fouling
PostPosted: Thu Jul 11, 2013 1:25 am 
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Joined: Sun Nov 07, 2010 10:54 pm
Posts: 425
Location: Brisbane
Yes 40mm with the pumps disconnected.
Exhaust is open (ish). 900ie cams, flowed heads.
No hesitation without the pumps, and around town it's better without the pumps mucking up the mixture.
Very little or no difference without pumps.

I'll pull a carb off and tell you what works for me as soon as I get a chance.


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