[Raymond]

The Bullet is running well but I know it could & should be better. Lopes along nicely on small throttle, easily does indicated 55-60 mph which is all I ever ask of it. But faced with a hill or a head wind, open the throttle a bit more and it get's louder but not much more go. Closing the throttle actually gives a brief extra push. Makes me think the mixture goes too weak with more throttle?

Postie delivered these today:





There's two new pilot jets, two new mains and a new emulsion tube. I think that is what I have generally called a needle jet in the past.

At present, the carb - that's the Mikcarb VM28 - has a 25 pilot, 117.5 main and AFAIK standard emulsion tube. Purchases are 27.5 & 30 pilots, 120 & 125 mains and a P0 richer emulsion tube. Have a needle clip on back order, in case the one in there breaks or flies away never to be seen again. Well, could happen.

Obviously, the plan is to have a play and see whether a richer set-up will improve things.

Depending when the Salt arrives, all this might have to wait for a few months . . .

[stinkwheel]

Now I'd have said picking up when you back off the throttle was a sign of running a bit too rich so maybe wanting a smaller jet or dropping the needle a notch.

However, trying larger first is a safe option, I'd rather be too rich than too lean.

[Raymond]

Now I'd have said picking up when you back off the throttle was a sign of running a bit too rich so maybe wanting a smaller jet or dropping the needle a notch.

However, trying larger first is a safe option, I'd rather be too rich than too lean.

Oh, dear, this is the problem with trying to tune the carb. Is the mixture too rich or too weak? Pity you can't just ask the engine. Don't think I'll be doing flat-oot plug chops either.

[Adrian II]

Pity you can't just ask the engine.

Can't you?

https://www.gunson.co.uk/product/G4074/Colortune-Single-Plug-Kit-14mm

Will need a long-reach adaptor

https://www.gunson.co.uk/product/G4055D/Colortune-Adaptor-Kit-14mm-Long-Reach

A.

[Raymond]

Yes, I have seen reference to Colortune plugs before. In fact, I think we used one on a Z750 I ran back in 1984. I'm being fussy, I want to know why the engine holds back, or rather, doesn't give more power in real-world riding situations. Best I can think of is experimenting with jets.

One downside is the expense. It's not cheap to buy a pocketful of carb jets.

I thought if the bike feels, fluffy for want of a better word, as the throttle is opened wider but gives a little shove of torque as it's closed that might mean it was too rich.

Came across this guidance on one site offering carb guidance https://support.shoptjbc.com/article/22-how-to-diagnose-rich-and-lean-conditions

Lean Mixture Symptoms - It is difficult to apply the throttle quickly or the engine picks up speed when the throttle is rolled off.

[stinkwheel]

You can buy cheap chinese jets on ebay which come as a kind of a selection box with say 10 jets covering everything in a certain size range. I use these to dial in the setup then replace the final size with a proper one.

[Karl Childers]

Can't you?

https://www.gunson.co.uk/product/G4074/Colortune-Single-Plug-Kit-14mm

Will need a long-reach adaptor

https://www.gunson.co.uk/product/G4055D/Colortune-Adaptor-Kit-14mm-Long-Reach

A.

Will that have enough clearance with a higher compression piston?

[Raymond]

Thank you for the suggestion Stinkwheel - I may end up looking for those cheap jets.

In my previous post, managed to confuss meself - should have written but gives a little shove of torque as it's closed that might mean it was too weak.

But you probably knew that was what I meant.

Maybe it's like an accelerator pump in reverse - when you reduce the throttle, the air supply is cut immediately but the petrol briefly keeps flowing at the higher level?

[Raymond]

Karl, we crossed in the post. I assume my 500 has a lowly Indian cast piston.

[stinkwheel]

Maybe I have the wrong end of the stick too.

For those sets of jets, I just use mikuni ones, so if you search VM28 main jets, you should come up with a few. Check the pictures too because they often mislabel stuff.

I have no misconceptions as to their quality and accuracy, you get 10 for the price of one proper one but it's super handy for chopping and changing to get things in the right ballpark, THEN move onto the more expensive ones..

[Adrian II]

Will that have enough clearance with a higher compression piston?

The 500 Bullet has a long reach 14mm plug, but the Gunson probe is actually like (and acts as) a short reach 14mm plug. Not quite sure why it needs an adaptor, as that would only move it further from the combustion chamber, but the manufacturer says it needs one!

A.

[Karl Childers]

Raymond: Sorry for the confusion, I think about getting a color tune unit now and then, my Bullet has a higher compression piston in it, that's why I chimed in.

Adrian: Thanks for that additional information.

[Raymond]

No worries, Karl.

I'm looking forward to playing with jets, after all I bought this bike for tinkering as it never fails to remind me, but that might not be for a few months yet.

[tooseevee]

Yes, I have seen reference to Colortune plugs before. In fact, I think we used one on a Z750 I ran back in 1984. I'm being fussy, I want to know why the engine holds back, or rather, doesn't give more power in real-world riding situations. Best I can think of is experimenting with jets.

One downside is the expense. It's not cheap to buy a pocketful of carb jets.

I thought if the bike feels, fluffy for want of a better word, as the throttle is opened wider but gives a little shove of torque as it's closed that might mean it was too rich.

Came across this guidance on one site offering carb guidance https://support.shoptjbc.com/article/22-how-to-diagnose-rich-and-lean-conditions

           Do you know Jets R Us?

                https://www.jetsrus.com/

[tooseevee]

Raymond: Sorry for the confusion, I think about getting a color tune unit now and then, my Bullet has a higher compression piston in it, that's why I chimed in.

Adrian: Thanks for that additional information.

           I have a Gunson & have used it on the '08 AVL with Mikuni TM 32. I used it a few years ago to second-guess myself dialing in that carb. All it showed me was that I had my idle to upper mid-range as good as possible already. You still have to do your WOT tweaking (Main jet).

           Does anyone out there want it? Only used once