Author Topic: Vision carburettor probblems.  (Read 2179 times)

motoracer8

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Vision carburettor probblems.
« on: June 20, 2014, 10:36:01 PM »
 Everyone here has been around the block with carb issues. And I must say the best cure for carburetor probblems is a good ignition system.

 I've played with British motorcycles for many years and so many owners of British bikes hate Amal carburetors for the wrong reasons. Ol Joe Lucas made notorious weak ignitions, so when the carbs started to wear and got alittle sloppy there wasn't enough juice to start the fire but the carbs were always to blame.

 Put a good hot ignition on a British bike it will start and run like a Honda even with worn carburetors.

 Whats that got to do with a Vision? They suffer from the same issue. Weak spark. Yeah it's got electronic ignition, all that does is act as the points and advance for the crummy coils, and now they're 30+ years old. Add that to the well known carburetor issues. Hard to start, runs on one cylinder, won't start when hot.

 When new they started and ran ok but now that they're 30+ years old things get tired. The starters draw too much current and don't leave enough voltage for the ignition to fire the weak coils. The ign unit needs about 10.5 to 11 volts to work, A good battery is needed. Motorcycles have resistor plug caps, they get old and have high resistance or are open and won't pass any current.

 Check the plug caps, they should have about 5,000 ohlms resistance, I checked many that were open. It takes a hot coil to overcome a high resistance or open plug cap and the Vision ain't got em.  NGK plug caps are cheap # VBO5F are the ones. While you're at it get some new plug wires, 7mm wire core automotive plug wire. Help those old weak coils get some juice to the plugs.

 No resister spark plugs with resister plug caps, too much resistance= weak spark.

 So make sure your ignition system is doing the best it can and it may overcome some of the carburetor probblems.

 Ok, I'll step off my soap box now.

 Ken

 

 
83 Vision and 11 others, Japanese, German and British

QBS

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Re: Vision carburettor probblems.
« Reply #1 on: June 20, 2014, 11:56:06 PM »
Amen Bro.  Preach on!

fret not

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Re: Vision carburettor probblems.
« Reply #2 on: June 21, 2014, 01:43:37 AM »
Is there a good replacement for the original coils?  How hard could this be?

Ignitech in the Czech Republic offer some hope for finding newer electronic controls for older bikes. (and modern ones too, as well as racing applications)
They also offer fuel injection.  I think they could be helpful if asked nicely.
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Rikugun

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Re: Vision carburettor probblems.
« Reply #3 on: June 21, 2014, 10:05:54 AM »

 
Quote
No resister spark plugs with resister plug caps, too much resistance= weak spark


I'm not sure what you mean by this.... The covers you recommend are 5k. The wires and plugs (I'm guessing?) are non resistor. What is different from stock?
« Last Edit: June 21, 2014, 10:14:23 AM by Rikugun »
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motoracer8

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Re: Vision carburettor probblems.
« Reply #4 on: June 21, 2014, 10:16:03 AM »
 Sorry if I was not clear. Do not run resister type plugs with resister plug caps..

 D8EA or DP8E is the correct plug.
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motoracer8

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Re: Vision carburettor probblems.
« Reply #5 on: June 21, 2014, 10:30:37 AM »
 Mike, I'm sure there are better coils out there, but better coils draw more current, and that passes through the control unit. And the really cheap transistors that switch the current on and off over heat and fail. I'll bet there's not $5 worth of parts in the entire box.

 I think Electrix is the company you are thinking of. They make control units with better quality parts that would probably support better coils.
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fret not

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Re: Vision carburettor probblems.
« Reply #6 on: June 22, 2014, 01:43:37 AM »
Didn't find Electrix but here is the link to Ignitech  http://www.ignitech.cz/en/
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pullshocks

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Vision carburettor probblems.
« Reply #7 on: June 23, 2014, 09:01:12 AM »
Very true, Motoracer.  My chronic slow-return-to-idle "carburetor" problem went away when I replaced my R/R and restored consistent voltage.

Once battery voltage dropped below a certain point it would start dying at idle.  However I could crank the idle adjuster way in and it would idle, at the same voltage.  In hind sight I see this is what was going on.

Eventually the charging problem got worse to the point that the bike would not restart after riding for a while.  I traced this to the R/R.  After replacing, there is no more voltage drop, and idle speed was 3000 rpm.  After readjusting the idle back down, the slow return to idle problem was gone



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Rikugun

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Re: Vision carburettor probblems.
« Reply #8 on: June 23, 2014, 09:21:33 AM »
Quote
My chronic slow-return-to-idle "carburetor" problem went away when I replaced my R/R and restored consistent voltage.
When I read this I went huh? Then you followed up with:
Quote
However I could crank the idle adjuster way in and it would idle, at the same voltage.
and I said "ooohhhh"    :)  Interesting!
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motoracer8

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Re: Vision carburettor probblems.
« Reply #9 on: June 23, 2014, 09:56:04 AM »
 Most electronic ignition systems have a low voltage threshold where they won't fire the coils. The Boyer units I've used on British bikes for years require a minimum of 11 volts, anything less no spark.

 The old points and coil system, if there was some voltage available it would make some spark.

 You need a good battery and charging system for electronic ignition to work.
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pullshocks

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Re: Vision carburettor probblems.
« Reply #10 on: June 23, 2014, 11:06:34 AM »
Maybe I will disconnect the charging system and let it idle , to see how far the voltage has to drop from full charge before the idle issues set in.  Pretty sure it is well before it gets to 11.

By turning in the idle adjust, you are opening up the butterflies, presumably this effectively bypasses the pilot circuit and brings in a richer, easier to ignite, air fuel mixture, eh?

Bottom line, good charging system, good battery, clean connections everywhere, like Motoracer said

supervision

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Re: Vision carburettor probblems.
« Reply #11 on: July 25, 2014, 10:15:24 AM »
The CZ ign. company has coil on top of plugs for tci ignitions for only $35 each. They don't say the ohm on those, but they do list some other tci coils one is 0.8 ohms, the other is 3 ohms.  The other day I heard Craig Rogers, owner of Rogers Racing, say his (Jared Mees number 9) Harley XR750 racer  uses the CZ ignition, which he said is the best they know of.
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jefferson

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Re: Vision carburettor probblems.
« Reply #12 on: July 26, 2014, 03:03:37 PM »
I am running a pair of Nology coils on the racebike. They were easy to mount and have had no problems. That bike has no charging system and just runs battery voltage though.  What affect that would have on the transistors in the cdi unit I have no idea. Just wanted to let people know it can be done and it wasn't hard at all, but that only applies to mounting the Nology coils. Other coils mount differently I'm sure.

QBS

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Re: Vision carburettor probblems.
« Reply #13 on: July 26, 2014, 05:52:22 PM »
All the TCI box wants is appropriate voltage.  Where it comes from and whether or not that source is replenished is irrelevant as long as its got approx. 11+ vdc.

supervision

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Re: Vision carburettor probblems.
« Reply #14 on: July 27, 2014, 11:10:37 AM »
 Thanks Jefferson, that's good to know.
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