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Learning how to build Lotus Seven replicas...together!
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PostPosted: March 30, 2019, 8:32 am 
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Joined: September 22, 2005, 8:12 am
Posts: 1622
Location: 4AGE in S.E. Michigan
It might be possible to find an accelerator pump kit used on large twin and 4 cylinder bikes 30 years ago. They were retro fitted to the float bowl drain plug, i.e. fuel supply and you had to actually drill a hole for fitting into the carb body for the accelerator discharge jet. You would also have to make linkage. Do not know if any one still make the kits. Might try some of the MC forums. Davew


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PostPosted: March 30, 2019, 8:15 pm 
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Joined: December 29, 2007, 10:41 pm
Posts: 896
Location: Vancouver, BC
I had a better look at the spare/ parts carbs, and as it turns out they do have progression holes. I had dear old dad look at them earlier in the week to see if they were present, but I'm guessing he needs some glasses :)

So, the plan is now to find some larger pilot jets. The ones in the parts carbs were 40s, and it looks like I can get sizes up to 60. I had to replace the thermostat housing and do a few other jobs today, so no time to mess with the carbs on the car.

Miatav8,
Yes, the carbs are keihins from a Honda cbr900. When I first got them they were cheap but a set off Ebay will now cost about $150.

Horchoha,
No accelerator pumps etc. They work sort of like an old SU carb but have a bit more refinement. Actually, they're more like a dcoe Weber crossed with an su.

But, if I can't get these things working properly I have two options. I have a spare set of DCOEs or I can source a speeduino and fuel pump and go injection as there's a set of throttle bodies taking up shelf space.

Rod


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PostPosted: April 6, 2019, 1:10 pm 
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Joined: October 11, 2006, 4:49 pm
Posts: 605
Hello Rod.

Great looking project.

The flat slide carbs on my FZ1 had poor off idle response. There are known fixes for this bike such as:

Backing out pilot needle to almost max.. you may find this under a brass plug.

Cutting the slide springs. I did mine 1/2 inch.

Drilling out the slide bypass holes. Allows the slides to move faster.

One jet kit calls for the fuel port closest to the butterfly to be enlarged.

Of course this sorts the lean condition at idle and low throttle openings. EPA mandates these things are lean at idle and rich at high rpm.

Perhaps a lambda sensor at idle would indicate rich or lean off idle stumble.

Keen to see how this gets sorted.


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PostPosted: April 8, 2019, 10:02 am 
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Joined: December 29, 2007, 10:41 pm
Posts: 896
Location: Vancouver, BC
Well, I can report that switching from a 40 pilot jet to a 50 has cured the off idle stumble. The car is now very easy to drive, though getting in and out is still difficult. Now I just need to tidy the thing up and put some miles on it.


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PostPosted: April 8, 2019, 10:30 am 
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Joined: November 11, 2013, 4:47 am
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Location: No. Nevada
Quote:
though getting in and out is still difficult


Price of admission, and keeps the riff-raff away! :wink:

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