Shot 750 carb slides

TeddyG

TeddyG

Hero member
Location
Portland Oregon
It appears these slides are shot- probably from the PO running it w/ a broken air filter and a contributing cause to it not idling for me (among other things I've been finding). Supposedly has 15K miles. My question is if the wear on the bores is marginal- the other side of the bores looks good. I'm ordering a rebuild kit along w/ other service items.slides.png
 
A good test is a finger into the inlet throat and feel how much backwards and forwards rock you feel in the slide. There shouldn't be much movement. No idea what the fix is as fitting a new slide in a warn body isn't the best. I tried getting my old 350 Husky Del teflon coated and that worked really well reducing friction and taking up some wear. So I tried the same on my 3c, not so good. For some unknown reason the coating blistered destroying the slides, one expensive failure.
 
With or without air filter doesn't make that much difference, unless you're regularly traversing deserts.

The zinc alloy that these bits are made of isn't renowned for its wear capabilities, just for ease of casting/machining. Petrol doesn't offer much in lubrication, zinc on zinc simply doesn't work for very long. As long as you haven't a defined arc-shaped ridge near the bottom where the slide mates to the mixing chamber, all will be fine. New slides aren't much better...

piet
 
if it wont idle for a fortnight, (not a good idea since oil circulation at idle is very weak) then I would suggest that you carbs are not synchronised, what instrumentation do you use to achieve that?
CLEM
 
Thanks guys- with the slide about half way down the inlet, there is some back and forth rocking, so I'll consider new slides, although I agree about the internal wear on the bores negating that. So far I've only started the bike for a short time when I received it, and it wouldn't hold an idle w/o the choke. I'll start it up after the oil is changed and various service parts installed (air filter, new cables, new fuel petcocks, cleaned tank, etc). I'm sure the carb settings need adjusting along w/ synching.
 
Those slides are absolutely fine - in my early days of (young, ignorant, poor) ownership I replaced my slides when they had literally worn through on the inlet side (you don't show that side in your pics). It still idled even with that amount of wear - it probably used to 'hang' a little before dropping to idle.
Years later the bodies were well worn and I rebored them, fitting hardchromed bronze slides I made myself, partly as a learning experience in a hobby machinist course I was doing.
 
so I'll consider new slides,
Click to expand...
As only a new type of slides are available, note that they have to be modified
to fit the old carbs. Clearance has to be at least 28,5 mm.
See picture, speaks for itself.

Ernesto
 

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Thanks guys- I'll going w/ the consensus and keeping the slides- just trying to do what's needed so that it idles next time I start it up. ChrisK- please explain where the fibre washers should be under the vacuum gauge screws. I've ordered a gasket rebuild kit including float needles and valves.
 
In your picture with the two carburettors in it, taken from above the carburettors, you can see a slot headed screw on the flat surface of each carburettor. These can be removed for fitting spigots to attach the hoses if you want to use vacuum gauges for synchronising.
 
Tippie said:
In your picture with the two carburettors in it, taken from above the carburettors, you can see a slot headed screw on the flat surface of each carburettor. These can be removed for fitting spigots to attach the hoses if you want to use vacuum gauges for synchronising.
Click to expand...


chrisk said:
From the pictures, it looks like they have no fibre washers under the heads of the vacuum guage screws.
Click to expand...

And refitted with fibre washers to ensure an air tight seal.
 
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