Author Topic: carbs and rebuild sets  (Read 241 times)

Offline Arfa

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carbs and rebuild sets
« on: May 27, 2022, 06:50:40 PM »
My custom is to drain the tank and the carbs (plus change the oil and filter and ....) before laying the bike up for the winter. Pretty much every spring when refilled I then get an overflow from at least one of the carbs. So this year I thought I'd steal a march on it and remove the carbs in spring, check that the float mechanism is OK and job would be a good un. Armed myself with a set of Nurse Julies best O rings just in case and here we go.
At some point in the past (18 months?) I'd gone for a carb rebuild with the usual kit of parts, most probably from DS. I'd found that the dimensions of the float valve assembly (needle and housing) were such that the assembly didn't work, so I'd carefully cleaned all the old bits polished out the slight ridge on the needle tips, refitted and reset the float heights. I had used the rest of the bits in the kit including the slow running jets. Subsequent to this I had great difficulty getting the slow running mixture anywhere correct- too rich.
So fast forward to this spring, I dug out the old slow running jets, cleaned them and refitted them in place of the "new ones". I also checked float heights again and also checked the float valve function. Guess what? Yes I had an overflow from number one carb- smart tap with hammer handle fixed that. On the stock setting for the idle mixture screw things seemed fine and later riding and tweaks including plug checks show that mixture is fine.
I didn't check the jet diameters physically but evidently the new idle jets were too large so out of an overhaul kit neither idle jets nor the float valve assembly were fit for purpose, nurse Julies O rings are much better than those in the kit too. Thinking about it only the needle, needle jet and slide (or body) might wear, the jets themselves aren't really subject to any wear in the normal course of events. So, I can't see myself replacing anything else soon. However, for the benefit of others, do the assembled luminaries on this forum have any good suggestions for carb overhaul hardware?

Offline K2-K6

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Re: carbs and rebuild sets
« Reply #1 on: May 28, 2022, 10:24:16 AM »
Your experience appears in line with more general and evolving view on forum that the original brass parts are hard to match in quality and accuracy.

Possibly not always salvageable in some projects but highly desirable if available in good condition.  That accuracy of original jets comes up often along with poor physical fit for some components (thread sizes one of them) certainly makes them a primary choice with diligent cleaning.

Perception, but lower sulphur fuels appear to make smooth action in things like the taper seat level control valve more problematic in these system too. Unsure there's a way round that,  but consider some oil adative in low proportion to assist this, in the area of 100:1 mix ratio (10ml per litre of fuel to make easy calculation) which may give enough change to reduce this occurrence.


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