SOHC.co.uk Forums > CB750

Got it running but got some problems

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UK Pete:
There are many things that go wrong with the pump, the rubber diaphram split or perished, the ball bearing pump valves get seized, the spray nozzels blocked, best thing is to have the carbs off and upright with fuel in the bowls, then open the throttle mechanism and see if it is squirting from the jets, there is loads of info on sohc/4 site and here http://www.hondachopper.com/garage/carb_info/accelpump_valve_repair/page9.html
The jets are a push fit you protect them with a bit of leather just grab pull and twist them with a pair of grips and they shoul come out
hope this helps
pete

Robbo:
Thanks Pete, you're a gent

UKROBK7:
If there is fuel coming out like that I would look at the float needle valves and then float height but I would have thought that fuel would be seen coming down the overflow pipes.  (1 of my carbs, however, was "fixed" by a previous owner by raising the internal overflow tube with a piece of plastic sleeve making the tube about an extra 10mm high instead of changing the badly scored needle)

Just rebuilt my k7 carbs and pulled the slow jets by locally heating the bodies using a hot air gun (the small one for heat shrink tubing) but they still needed a lot of force to get 2 of them out.  Glad I did, 1 of them had completely blocked side holes and another had them partially blocked.

I also found my accelerator pump ball valves were corroded and I replaced those with stainless plus a new diaphragm, now the valves work as they should.

Rob

Robbo:
I had the carbs apart last night in my workshop:

The BB and spring on the accelerator pump were missing, I made a handy replacement with the end of a pop rivet and a home made spring - it works a treat!

I pulled the pilot jets out and gave them a good clean - there was so much s**t in there that I used a 1mm drill bit to clear the main hole out.

Set all the float heights - hopefully they won't leak anymore (but I will hook them up to a tank to check before I put them back on the bike)

I'll let you know how I get on this weekend

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