Bonneville America Forums Forums Technical Forums Performance Mods Balance Woes

Has anybody installed a hex head bolt in place of the factory carb balance screw? Looks to me like it would make adjustments much easier to use a wrench rather than a 90 degree screwdriver. Also, It seems like I have to balance my carbs way too often. Does anyone else have a problem with their carbs staying in synch, or have any idea why I do?

I don't believe anyone has changed it out, probably because no one has sized it yet!

What balancer do you use and how far out are they showing? Can you also qualify 'way too often'?

I'm using a Motion Pro SyncPro. I'm not convinced that is a great product, and would rather have a mercury type tuner, but don't want to shell out another $100 or so. I can feel performance problems (ie surging), seems like every week, maybe two, and find carb synch fixes it.Usually takes only a tiny tweak, maybe 1/16 turn.

That screw's a mystery to me.
It looks like M4-.7, but one of those goes in 3/4 turn & stops.

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Also, It seems like I have to balance my carbs way too often. Does anyone else have a problem with their carbs staying in synch, or have any idea why I do?

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Vacuum leak????
Lots of places to check for this, vacuum caps good and tight, no cracks?
Manifold inlet rubbers tight and in good shape?
Unless you fiddle with the carbs, (jets etc) you shouldn't have to re-balance much at all.
Almost forgot.....exhaust header bolts tight? They've been known to loosen. Plugs tight?
The tops of your carbs that hold the diaghram down....are the diaghrams seated properly?

Ok, so this is probably a dumb question to some but, can someone tell me where I could get the vacuum caps?

I had a look at mine and one of them is cracking so I think it might be time to replace them. I would appreciate anyone who can help even if it means my getting a bollicking

Looking at my metric taps I see there is such a thing as M4-.75.
Maybe that's what it is.
Don't know why they'd use a coarser thread on something that touchy.
& don't know why a 4mm balance screw would be different from all one in the carb bodies.
But, maybe.

cheers Ed. I thought as much but wanted to check with someone who had done them already. I was also thinking about my dealer but too far away, he'd probably have to order them (too long to wait) and he'd ask too much for them also.

I think I like your idea better

Just wanted to let you all know that I changed one of my vacuum caps that was showing signs of cracking. Well what a difference. I think over a period of time I may have got used to a bit of an increasing amount of air entering a carby and thought, my bike just needed a tune. Well my speedie is running much smoother now so it's certainly worthwhile checking this one. I also found that the offending rubber stopper was different to the other 3 and probably put on there from a numbskull dealer mechanic. I tell ya, my experiences with bike mechanics whilst only short is way less than satisfactory. So much better to do this stuff by yourself than letting some bored and lowly paid grease monkey who having done the same thing day in day out, just doesn't give a bug*er. What's even worse is they charge you for the priveledge. Gee thanks Mister If I talk to you nice, can you continue to over charge me for really *hit work next time I haven't a clue about anything mechanical on my bike. Anyway, the one I replaced it with was a shorty too but without cracks.

Sorry guys, it gets going when I think about mechanics and some of their bad workmenship. Only 3 months ago I got one of these idiots when changing my tyres to replace the front brake pads. Not only did he scratch my rims but also, he put two different thickness pads on each side of the rotors. No, they weren't used but I suspect one was from a speedmaster and one from an America. At least that's the bullsh*t they tried on me. Whatever, won't be going back there again.

just looked at my bike. I have 1cap shorter than the other 3 it is the only one that is dry rotted.

Interesting. I wonder if all our bikes have the same configuration where 3 are longer and appear in good nick whilst the shortie is the normal "offender" with cracking etc It didn't make sense to me really. I like the long ones. They appear to be higher quality rubber and easier to take off too.

Not sure if this answers your question but...
3 of the vacuum port caps are there as fitted by Triumph. The 4th (LH front on mine) is where the pipe from the AI pump would go. If the AI system is removed, that 4th port would have to be capped; apparently, the Triumph rubber is of a good quality and tends to outlast replacement rubber. Does this relate to your situation?

Note: I can't take credit for this, I've gleaned the information from these forums. :]

You're right echo.. Normally the AI is hooked to one of the vacuum ports. The one supplied by AI removal kits is of a different size. But a caps a cap as long as its not leaking and fits tight. Or you can hook um together with a length of tubing. Whatever strikes your fancy. I think its probabaly a good idea to replace them at least every couple of years. They become brittle from heat off the engine.

It could be my imagination but I thought my engine got a wee bit smoother when I linked the carb ports with a single piece of tubing. Anyone got any idea how long the manifold rubbers are good? I'm beginning to suspect the ones on my '01 are leaking air...might just go ahead and replace them and then I'll know for sure.

Yes Neill, that's spot on mate.

FYI, I replaced my A1 with a kit this time last year and forgot (and still can't rember -oldtimersdisease ) the kit probably did come with a stopper for the left front. If so, mine only lasted less than one year and if that is the case, perhaps anyone else who have replaced their A1, should look at that little bu#ger of a stopper themselves. Like Neill says, the Triumph stoppers are of high quality and perhaps, and it looks this way, other stoppers are just inferior quality which leads to the probs I and others have experienced.

Also FYI, I just ordered 4 new rubbers stoppers from my dealer just to firstly, replace the left front with a similar stopper to the rest and secondly, to have spares knowing how important they are.