Author Topic: Velo Viper  (Read 566 times)

Offline Oggers

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Velo Viper
« on: May 02, 2022, 08:30:34 AM »
Gents

Checking the oil level in the gearbox of my 1958 Velocette Viper, I found green khaki stuff oozing from the level plug. Feeling I ouught to be better safe than sorry, I drained it and put clean GP50 in. Any ideas what this stuff is? I assume some sort of specialist gearbox oil?

Gearchange feels a little notchy also. Nowhere near as smooth as the MSS - clutch adjustment perhaps?

Bike seems to run OK, but on idle it remains on high idle after a run, then settles down, then occasionally stalls. I have fiddled with the idle and the air mix screw, and cleaned the latter out. No real difference. No discernible air leaks either. I seem to recall this being a symptom of a poor mixture. Can anyone confirm please?

Offline Mark M

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Re: Velo Viper
« Reply #1 on: May 02, 2022, 08:45:42 AM »
I'd check the slide to carb bore fit, this is a classic symptom of worn slide and or body. As it happens I have a Monobloc carb body with correct numbers for a Viper which you are welcome to cheap as it's in my autojumble box and didn't sell last week!
REgards, Mark

Offline iansoady

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Re: Velo Viper
« Reply #2 on: May 02, 2022, 09:57:00 AM »
The green stuff is probably water in the gearbox oil. If the rubber boot on the clutch cable isn't in good condition water can run down the cable into the box.

If you can't find an air leak I'd probably agree with Mark re worn carb.
Ian
1952 Norton ES2

Offline Oggers

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Re: Velo Viper
« Reply #3 on: May 02, 2022, 10:52:25 AM »
Ian

Yes - I thought it was emulsified oil also - hence the change. Boot looks fine. All a bit odd.....

Ref idle - yes worn bore/slide makes sense. I'll give it wiggle and revert if it moves about.....

Offline Oggers

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Re: Velo Viper
« Reply #4 on: May 02, 2022, 11:06:54 AM »
I have just poked my finger into the carb intake and wiggled the slide. There does appear to be movement. Mark M - what do you want for your body!

Offline Mark M

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Re: Velo Viper
« Reply #5 on: May 02, 2022, 01:20:22 PM »
Oggers, I have replied via the forum but you can also email me at trials59(AT)yahoo(DOT)co(DOT)uk
REgards, Mark

Offline iansoady

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Re: Velo Viper
« Reply #6 on: May 02, 2022, 03:37:46 PM »
You usually detect most movement if you open the throttle slightly as it can move less when seated on the bottom of its travel.
Ian
1952 Norton ES2

Offline Rex

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Re: Velo Viper
« Reply #7 on: May 02, 2022, 04:53:10 PM »
Big singles can wear out their carbs surprisingly quickly and I usually consider carbs to be consumables now, unless the particular carb is excellent in this respect.
 With all due  respect to Mark M's offer a quality bike like a Viper would get a new carb if it was mine.

Offline Mark M

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Re: Velo Viper
« Reply #8 on: May 02, 2022, 06:35:08 PM »
I've had this carb in my autojumble box for a few years, it's rather dirty and other than identifying the flange number against the Amal catalogue I've not paid it any attention. While checking it out for Oggers I popped a near new slide in it and blow me it's a very good fit. If I'd known I'd have put it aside for one of my projects but I will honour the deal!
REgards, Mark

Offline Oggers

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Re: Velo Viper
« Reply #9 on: May 09, 2022, 08:48:42 AM »
Gents

I have pulled the top off the old carb (Amal monobloc 376) to inspect things and the slide looks new and the bore does not look worn or scored. There is for sure a very slight amount of play, but I can't believe it is significant. Before I tinker about with the replacement carb, is there anything else I should be looking at for causes of a rough idle? So far, I have cleaned the idle air passage, the mix screw, the pilot jet, checked the gasket and faces to the head. Anything else carb related I should look for? Anything else non-carb related I should look at perhaps? Spark seems OK - mag overhauled not long ago..... 

Thanks as ever

Offline murdo

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Re: Velo Viper
« Reply #10 on: May 09, 2022, 09:22:15 AM »
How is the valve clearances?

Offline Oggers

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Re: Velo Viper
« Reply #11 on: May 09, 2022, 09:24:43 AM »
Valve clearance seemed OK last time I checked.....I'll take another look whilst the tank is off.....

Offline R

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Re: Velo Viper
« Reply #12 on: May 09, 2022, 11:39:17 PM »
So far, I have cleaned the idle air passage,

Getting those idle air passages clean is a mission, that for sure.
Cleaning it once may not be enough.

I had a pair (concentrics) on a Commando that had apparently stood out in the rain for a few years ?
A new pair of carbs gave a good idle, so I set about getting the old carbs to that state.
I think after 6 or 7 cleans, they came good. !
That white corrosion gets attached to the walls, and one clean won't be enough ?

Offline Oggers

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Re: Velo Viper
« Reply #13 on: May 10, 2022, 09:44:04 AM »
Well - valve clearances are miles out. At least 14 thou on ex - should be 8. Inlet to check. This may be the root cause of the rough idle. I have not actually checked these - my mistake, as I was thinking of the MSS which of course is similar -  but I was assured by the PO that all was good. Clearly not! Makes me wonder about the timing now!

Offline R

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Re: Velo Viper
« Reply #14 on: May 10, 2022, 11:22:05 PM »
So your next post will be about setting the timing correctly ...

NEVER take the word of the PO as gospel. !?
Some folks will say anything.
Some folks just don't know anything ...
« Last Edit: May 10, 2022, 11:23:38 PM by R »