Triumphrat

IrlMike · 12-28-2012, 01:00 PM

Yeah, doing what you're doing it's definitely worth a go, even if there is some uncharted territory. Hell, I haven't got as good a reason & I'm still tempted, just for the 'craic' as we say here!

stephsride · 12-30-2012, 02:21 AM

I'm replacing my airbox tomorrow. Any advice on repairing the cracked rubber joint between the airbox and air chamber? Would any recommend duct tape? Or should I go for replacement part?

Also doing a tire change and bearing R&R for the front wheel.

Steph

IrlMike · 12-30-2012, 05:44 AM

That rear airbox chamber (the one behind the painted side panel) is not critical at all as regards engine performance or carburation. I don't think anyone has ever noticed any difference with it disconnected - tho' it's needed to mount the side panel & seat lock of course. It's probably there for induction noise tuning imo.

(The sealing of the two halves of the front airbox is a different story - that is very important for carburation.)

So with that in mind, duct tape, new rubber part or nothing at all are all options that won't affect the bike in any noticeable way.

stephsride · 12-30-2012, 11:40 AM

You're right Mike, you didn't answer my question!!!

Anywho, in doing my research last night, which consisted of keyword searching the forums, I came up on alot of discussion about pressure drops across interfaces, the airbox/carb intake being one of them, the other being the cylinders/exhaust, the root effect being the correct mixture of fuel and air for combustion. Before we get any further, I'll warn all of you that I've little to no experience overhauling carbs or engines. But I do understand concepts of pressure and temperature. And I have an engineering background if that helps.

So what I'm getting is that the air chamber /airbox interface is far enough removed from the critical carb intake interface, that no effect on performance is seen. Is that what you're saying Mike? FWIW I spent a few hours last night repairing the air chamber, using JB weld. You're right, I do want to keep it if nothing more than have a mount for the side panel. I did shove my camera phone into the airbox intake and captured a very dirty filter. I'm hoping that will explain why my bike seems to "engine brake" rapidly when the throttle is decreased. I was going to post the photos but for some reason couldn't find a way to do it. Perhaps I'm limited to 5 photos, or is it a hard space limit?

I also took photos of the wood mount I made for my Sears jack, as well as my bike sitting on it and strapped down and all.

Peace & Love

Steph

IrlMike · 12-30-2012, 12:55 PM

Quote:

Originally Posted by stephsride

So what I'm getting is that the air chamber /airbox interface is far enough removed from the critical carb intake interface, that no effect on performance is seen. Is that what you're saying Mike?

Sort of. Empirically (butt dyno), the rear air chamber didn't seem to make any discernible difference with/without. It's a Helmholz resonator, but I suspect it's not big enough to make much difference as regards volumetric efficiency (cylinder filling), so I surmised it's more to do with acoustic design. (Intake noise does factor is overall noise control. Or it could be there for more aesthetic reasons of noise quality - quite a big area in automotive design.)

The question of the resonator's location is also perhaps interesting. Maybe not so much distance, but the fact that there is an energy absorbing element (the filter) between the driving oscillator (valves opening & closing) and the energy storing element (the chamber). ie the filter is acting on both directions of the pressure wave.

I think the electrical analogy might be placing a resistor in an LC resonant circuit between the L & C, rather than at the input to the LC parallel elements?

The build up of dirt blocking the air filter element is trivial compared to shutting off the intakes near completely when the throttle butterflies are closed. So there's no noticeable engine braking effect from the air filter.

The effect of a blocked filter will be seen in reduced volumetric efficiency & richer fuel/air ratio delivered by the carbs.

(Lol - I though I had answered your question before ?

)

Randommech · 01-02-2013, 08:32 AM

Clubmans are now on due to a well informed Christmas gift from my Brother

Sent from my LGL55C using Motorcycle.com Free App

XeNoMoRpH · 01-02-2013, 09:24 AM

Interesting way of mounting them. Most other people would flip them and put them lower like this:

stephsride · 01-02-2013, 05:22 PM

Ok IrlMike, I completed the repair of my airchamber (aka resonator) with JB Weld and now am going for uncharted territory with carb overhaul. First question is, who other than BikeBandit supplies rebuild kits for Keihin carbs? Next, should I remove and clean the pilot screws, especially since it will require me to drill a hole in the caps?

Thanks,

Steph
PS. Random, how is your carb cleaning going? Any issues I should be aware of??

IrlMike · 01-03-2013, 06:12 AM

Steph

I've no experience of carb parts places in the US. Place called Sudco maybe? Thing is, these carbs are made for the bike manufacturer & aren't supported directly by Keihin (same with Mikuni) at all. However, jets & needles are common to other carb types & are available, sometimes some other parts.

Apart from cleaning tho', unless you have problems I wouldn't be replacing any parts, or gaskets either on the Keihins. Tho' buying new pilot jets is maybe a good alternative to trying to clean any hardened residues inside them (in really bad situations, main jets too). The EU bikes don't have the pilot screw plugs & are set a little richer from the factory which makes starting easier, hence the general advice here to set the screws about 2.5 turns out (removing plugs as needed). It's not too critical - if you have a tool to adjust with the engine running, an 1/8 turn or so either way can improve idle slightly by 'ear' (ime). Throttle balance with a vacuum gauge set is way more critical for idle & low throttle operation.

berkdogg · 01-03-2013, 07:19 AM

Clean that garage while you're at it.