VHB 30 Tuning question

[canuck750]

I finally got my V7 Sport out for its first ride of the year, fresh premium fuel (no ethanol), a strong battery, fresh NGK BP7RES plugs, started right up on choke, warmed up for five minutes and went for a ride to get it real warm.

I synced the carbs and then pulled the plugs, sooty already, more so on the right cylinder. I then fitted a colourtune to the cylinders one at a time, on idle and at 3500 rpm the flame is a bright orange.

I have stock jets in the rebuilt carbs, needle on second position (I dropped the needles to see if any effect and not much at all still orange flame), floats are old style and set to the right height. The mixture screws are turned out as per the owners manual, 2 1/4 on the left 2 1/2 on the right. Turning the mixture screws in and out did not have much effect on the flame colour. (maybe I have to turn the screws very slowly to notice a change in flame colour?)

According to colourtune I should have a Bunsen blue flame so it looks like I have the carbs set far too rich.

What is the best route to follow? swap the idle jets first to a leaner jet followed by the mains?

Thanks

Jim

[oldbike54]

 Probably rhetorical , any chance the choke slides are sticking Jim ?

 Dusty

[SeanF]

I don't think resistor plugs are specified for the old Tonti bikes, unless you have some non-stock stuff going on with the rest of the ignition system.

[oldbike54]

I don't think resistor plugs are specified for the old Tonti bikes, unless you have some non-stock stuff going on with the rest of the ignition system.

 Good point , and what type of plug wires , resistor or copper ?

 Dusty

[canuck750]

Good point , and what type of plug wires , resistor or copper ?

 Dusty

I am running copper core high tension wires, I can only get NGK resistor type plugs here (at least the places I usually source). The chokes are new flip types, I don't think the chokes are sticking. Ignition is a Dyna III. Carbs have been ultrasonic cleaned, several times. The bike runs ok on a steady throttle but the plugs get sooty at in town speeds. After a half hour in town riding the bike balks at low throttle until it clears its throat. 

I will pull the choke plungers tomorrow night and see how they are seating.

[JoeW]

Jim, Make sure the slides are as closed as possible to maintain an idle, then turn the mixture screws 1/4 turn at a time, wait a couple seconds between turns. Watch your flame and listen to your engine, it'll smooth out if you're headed in the right direction. If you do one full turn one way with no improvement or worse running, go the other way 1/4 turn at a time. If the bike starts idling higher, back off on the speed screws a little, 1/8 to 1/4 turn. Will the idle drop or even die if you run the mixture screws all the way in?

[Moto]

I synced the carbs and then pulled the plugs, sooty already, more so on the right cylinder. I then fitted a colourtune to the cylinders one at a time, on idle and at 3500 rpm the flame is a bright orange.

3500 in neutral or going down the road? The throttle opening to get 3500 in neutral is much smaller. Ideally, you'd be better off observing 3500 under a load, to approximate actual running conditions.

The basic idea is to tune for throttle position. I mark my throttle handgrip with a piece of tape and a wire pointer to show closed, 1/8, 1/4, 1/2, and full. Then I tune as per the Dellorto manual that references those openings. http://danskkartingcenter.dk/dellorto_motorcycle_carburetor_tuning_guide.pdf

I think the rule is to start with idle tuning, and then go up through the progression as described in the book: cutaway, needle position (and needle jet), and main jet.

[oldbike54]

I am running copper core high tension wires, I can only get NGK resistor type plugs here (at least the places I usually source). The chokes are new flip types, I don't think the chokes are sticking. Ignition is a Dyna III. Carbs have been ultrasonic cleaned, several times. The bike runs ok on a steady throttle but the plugs get sooty at in town speeds. After a half hour in town riding the bike balks at low throttle until it clears its throat. 

I will pull the choke plungers tomorrow night and see how they are seating.

 Not an expert on the Dyna , but here is what I think I know about ignition . The coils , plug wires , and spark plugs resistance need to match up fairly close . Lots of older bikes have the sooting up issues after the owners replace the plugs or wires with resistor type .

 Dusty

[acogoff]

     I would start over with BP6ES plugs.

[Chuck in Indiana]

Sounds like an ignition issue to me..

[canuck750]

As usual lots of great information, thank you!

Joe I will follow your advice on adjusting the mixture screw, I didn't notice or hear the engine making much difference last night while adjusting the screws.

I will swap to the #6 NGK plug and see what that does.

Chuck, can you elaborate on what you think may be the ignition issue?

Thanks again fellas.

Jim

[Curtis Harper]

Two main things in the VHB's that cause richness are the rubber oring on the choke jet being deformed, cut, smooshed or otherwise generally screwed up where it sits in the float bowl. The other is the rubber on the base of the choke plunger will get deformed and once it gets a ring in it, the brass hits the carb body and no longer seals the raw fuel out.

[guzzista]

Something like close to 40 years ago, my Ambo ( VHB square lide with central accell pumps, would blacken the plugs and emit sooty exhaust. The problem did not get solved till the pumps got new bits ( check ball, springs etc. ) Later new pumps were installed. May want to have a look see in there

[canuck750]

Two main things in the VHB's that cause richness are the rubber oring on the choke jet being deformed, cut, smooshed or otherwise generally screwed up where it sits in the float bowl. The other is the rubber on the base of the choke plunger will get deformed and once it gets a ring in it, the brass hits the carb body and no longer seals the raw fuel out.

Thanks Curtis! 

That gives me two more things to check, my flip chokes are original ( one would hope that they are still serviceable, they are hardly a day over 43 years old) where as the O rings are 'probably' new, can't be 100% certain but I will check them.

[Cam3512]

If you can't get non resistor plugs up there, hit me up and I'll send you a bunch.

[Chuck in Indiana]

Turning the mixture screws in and out did not have much effect on the flame colour.

Ok, you have one of two things. Overly rich from the chokes leaking fuel or weak ignition for whatever reason. The chokes are easy to remedy, so I'd fix that first and rule that out.
Do you have a bright blue spark?

[canuck750]

Ok I think I have had some success, first I stripped the carbs down, again, the underside of the choke plungers were hard and there was a ridge in the rubber so I swapped in another set that I had from another bike that are new.

The 'professionals' with the dyno put in 130 main jets last year so back in went the 142 mains.

Fired up the bike, let it warm up and the synced the carbs again. With the mixture screws set to the lean side of the factory recommended settings the colour tune was pretty much bang on. the left was a wee bit lean and the right a wee bit rich.

Pulled the plugs after and they look pretty good.

I then put in a pair of the BP6ES plugs (found a pair of non-resistor types, thanks for the kind offer Cam) and the burn was much more stable with a Bunsen blue hue.

Hoorah!

The bike idles nice and the engine runs up smoothly to 5000 rpm.

A big thank you to the collective brain trust out there, a consensus on the chokes and Curtis who zeroed in on the plungers not seating 100%

Jim

[oldbike54]

 Attaboy Jim 

 Dusty

[Don G]

I usually just make new rubbers with my hole punch set, have not had a problem with performance yet. DonG

[canuck750]

Today I got some time to try out the Gunson gas analyzer I bought as a mate to the colourtune



Straightforward instructions, easy to use don't know how accurate these are but spending a half hour testing the exhaust and the results were that the factory recommended mixture settings were pretty damn close to getting the idle colour of the combustion on the Colourtune and the CO % on the analyzer.

 I warmed the bike up on an hour ride, then pulled the fresh plugs - left a little lean, right a little rich, re-synced the carbs, set the idle and then set up the analyzer. With a target of 2% CO I adjusted the left to be a wee bit richer and opposite on the left. I got to a steady 2.4% on both sides, the bike idles better than it ever has and later when I pulled the plugs they look about right.

I don't know what to think of the Analyzer? is it worth the price? who knows I guess if I am following and understanding the simple instructions I have got the tuning about as good as I can expect on stock settings with a stock cam and carbs but running a KN filter.

Now just to ride the damn thing hard and enjoy it for what it is.

[centauro]

Not an expert on the Dyna , but here is what I think I know about ignition . The coils , plug wires , and spark plugs resistance need to match up fairly close . Lots of older bikes have the sooting up issues after the owners replace the plugs or wires with resistor type .

 Dusty

Larry from Dynatek (the makers of Dyna) once  told me that you either use resistor caps OR resistor plugs, but not both combined. Using both types together will likely overheat the coil, and/or results in a weak spark.