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Comet Carb'

cinquecento

Well Known and Active Forum Website User
Non-VOC Member
My goodness this little b*ggers been testing me today. Second shake down run after rebuilding top end and only hving aquired the machine several hundred miles previously.

After first short run 15 - 20 miles it was tighten up head oil feeds and leaks to inspection caps. Today having stopped after 3 - 4 miles to get fuel could I get the b*gger started, plug in,plug out, plug changed. Called recovery service after 30 odd min’s . Then with a bit more effort the b*gger fired up.

Cancelled recovery and headed back, had a mooch around it appears that the inlet rocker was slack. I had checked and rechecked when assembled as I was a little twitched about the the push rod not being properly seated in the cam follower. Anyhoos, adjusted checked and she fired up, I shut her down and tried to start again: everything sweet. Why not have a simple ‘rotate the pushrod ‘ like HD machines, to say ‘take up fore and aft movement’ does not inspire confidence in machining tolerences as there ought only to be up and down movement surely.

However, one thing that is apparent is the carb is p*ssing fuel, hopefully the pic has attached below. It seems that at the base of the carb’ body there is a screw on base that holds the main jet. I’m reluctant to unscrew at the mo’ as I don’t want to put force on the carb’ body while fitted to the manifold.
Any comments on what appears to be a chip pointed out by the red pointer or is this some kind of pilot air hole, also is there a gasket where the base screws to the carb’ body ?

Thanks in advance.
CometCarbBody.jpg
 

vibrac

Well Known and Active Forum Website User
VOC Member
I was always told the Vincent push rods are correctly adjusted if I can just turn them with my two little pinkies
If thats what hardly ableson rider instructions mean by "rotate the pushrod", well perhaps I have been wrong these last 40 odd years.....
 

cinquecento

Well Known and Active Forum Website User
Non-VOC Member
Ta' muchly.
Why is there such a deficit of carb’ literature and diagrams, is it thought that owners should refer direct component suppliers literature. But thanks for the pointer as I was considering a ‘soap’ gasket as the amount of fuel ‘bleeding’ through was causing concerns that with a carb’ blow back a fire hazard would be a concern.

Regarding the pushrod adjustment check; yes, that's it exactly, no slop verically or laterally but a nice free rotation, obviously my ' pinkies ' need a workout. Having owned old HD’s I would comment the accessibility is a problem with the Vincent/Irving? design but also I wonder why not use alloy pushrods, is it to do with lack of room for appropriately thick push rods.
 

chankly bore

Well Known and Active Forum Website User
Non-VOC Member
Make sure you get the correct gasket here as if it is too wide it blocks off a little connecting hole in the jet block. The gasket is shown, but not described on page 22 of the Rider's Handbook. On my machine, at least, the fuel level settles just below the air bleed hole indicated. Maybe lap in your float needle, fit an extra gasket above the float arm, slightly tilt the carburettor or do a dance with a dead budgerigar under the clothes line at midnight. Any or all the foregoing sovereign remedies have proved beneficial in my case. Cheers.
 

vibrac

Well Known and Active Forum Website User
VOC Member
One good tip I always wished id followed up was to use (archery) aluminum arrow shafts and tips to make push rods and then one day 'bingo' in a box of Vincent 'rubbish' I had bought there was a set
 

cinquecento

Well Known and Active Forum Website User
Non-VOC Member
would they not need another harder ' wear 'material at either end, i guess as long as this was an interference fit so they did not fall out on installation that would be OK. But then what dia' of rod would be needed and the quality of the alloy; there is such a variance.
 

nkt267

Well Known and Active Forum Website User
VOC Member
Yes..Anything from 16/13 to 23/14 depending on what spine and weight you need.A choice of all alloy or alloy/carbon(stiffer and lighter than the equivalent spine in alloy).then you will have to make hardened ends, also allow for the expansion rate. you may if you get it right hit Gold..John
 

Black Flash

Well Known and Active Forum Website User
VOC Member
I am sure in the world of Vincenteers there must have been many that tried to make alloy pushrods before.
I am also sure if they were any good or superior they would have been for sale from the ususal suspects for a long time.
From my point of view, better get your carb sorted and enjoy riding your fabulous Comet.
this summer ain't gonna last forever (... some hardrock band wrote that line 35 yrs ago)
Bernd
 

cinquecento

Well Known and Active Forum Website User
Non-VOC Member
could be right about getting the carb' tuned, it started spitting after abbout 15 miles yesterday and then gave up the ghost requiring recovery vehicle.

I think i'm being distracted by the valves going out of adjustment just because I found the inlet slightly slack yesterday and that this is the cause of my woe's. As you suggest I'll strip down the carb' to ensure all is clean and that the pilot jet is not blocked.
 
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