Carb tuning

[pearcey]

There's been quite a few threads on this now, but not much feedback.

Given that this sort of work should only be done if something else has changed - new exhaust system etc. Has anyone had any carb tuning done in Perth - i.e. rejetting, cleaning whatever and what was your experience? What I would like I suppose is to ride my bike in, have someone check the carbs, change jets etc. if necessary then ride home. Is there anywhere like this?

There was a place in the UK I used to go, where you basically booked your bike in for an hour on the dyno, and they sorted your carbs out there and then on the dyno - off you went. I think that as most new bikes are fuel injected now there's not so much call for it and most dynos don't do that sort of thing. Not sure if there's anywhere like that here.

[McGoo]

this thread is relevant to my interests. I have a question for someone who is very knowledgeable with carbs, happy to pay for answers, but dont know where to go.

[pearcey]

I spoke to one bike place, they basically said leave the bike with us, we don't know how long it'll take etc. Might be what I've got to do, but it means either 2 taxis or getting hold of a trailer (and a tow bar). Rather just ride in and ride out if possible.

[-Mark-]

I had my carbs tuned to suit a new exhaust. But in my case I purchased a kit (Ivans Performance in the USA) and just got my mechanic to install it for me. It is a shitty job for the mechanic, getting the carbs out of the bike and re-installing was no fun. Basically every time you need to make an adjustment or change a jet you have to rip out everything and then put it back again. This is why if you approach it with no "kit" to suit your application there will be a lot of trial and error hence a lot of labour. In my case the kit with the air box mod and the exhaust produced perfect fuelling and transformed the bike

[darkfibre]

What sort of carbs and how many?

The problem with getting carbs re-jetted in Perth is more the fact it would be a non profitable business.

Speaking as a mechanic here are some points. (we are talking about a proper rejet, not just a blind main jet swap)

1. Anyone who has the skills to do this quickly and efficiently will be asking at least $120 per hour - or they should be doing things that do pay that.
2. Jets - for ride in and out they need to carry the jets and needles in stock. There are at least 4 common brands of carbs, with many different models of carb per brand - thats 100's of hard to get components to have sit on the shelf
3. To rejet properly you need to know the mixture at different engine speeds and throttle openings - so we have before and after dyno runs. The time to remove, rejet and refit a set of quad carbs can be two hours. Do that 2 or three times and you have spent a $1,000
4. Its not always just one jet change - if you remove the air box on a CV carb style bike, you can get full throttle HP by changing the mains, but the low speed running will need other changes as well.
5. Unfortunately some people also want to rejet carbs that are already in need of repair. Trying to modify a carb with problems is a treadmill worse than dealing with the DPI.

Here is an idea of what the different jets do;
jet-chart.jpg

Personally, I would advise a lot of research on what others have done to your model bike, and use their experience as a base line to work from.

[McGoo]

...knowledge...

Where did you pull that picture from Darkfibre? Im trying to consult the web to answer my question, but Im having a hard time tracking down definitive information.

[JimmyR]

Well there's the bike doctor on Scarborough Beach Road. Anyone had experience there? He has a dyno.

[smokeymatt]

I believe i can help PM sent

[Rich]

Smokeymatt...saving Suzukis, one bike at a time...

[pearcey]

darkfibre - that's a great post - thank you. We're spoilt in the UK I guess; there's advantages and disadvantages of 60m people living in an area basically the size of Perth. The guys were just up the road from me and rented a place out in an industrial estate, they only did it in the evenings. They didn't even charge for parts, they just swapped the needles or whatever round with the ones they had. Double Take Dyno for anyone who's planning to relocate to Southampton! But there's loads like that in all the cities.

smokeymatt -thanks again and I'll be in touch.

[Mattis]

Russell @ Dynotime in Wangara use to do carbs back in the day - did a sterling job of fitting a jet kit and ignition advancer on a blade I use to have (included before and after dyno readouts). Also did a mates ZX9R and both bikes never rode better afterwards.

I don't believe he does carb tuning anymore thought (only EFI tunes) - probably due to the time it takes given its such a PITA job to do.

My R1 needs a jet kit fitted, ignition advance done and appropriate before and after dyno runs but yeh I haven't really chased any shops in Perth at this stage - might see if I can twist Russel's arm or if anyone else has contacts for someone who can do this work please feel free to pm me.

[pearcey]

Mattis - didn't know the early R1s had carbs. Nice.

[Cbr1k]

I have a bike with carbs. Trieds all sorts of fuckarounds and everything. You know the best thing is just to leave it at stock.

Unless you have a straight through pipe and pod filters stock is really fine.

The trick I found is to replace everything that you can. The tolerances for carbs are quite small and even small scratches or nick can change things. Replacing your pilot jets, needle jets, main jets, Emulsion tubes, Needle & float needle is relatively cheap and can solve a lot of problems. After tat you can tackle float height. Then do carb balance and valve clearances (should always do both together).

Also soak you CV rubbers in Armourall as they sometimes get stiff with age. Finally check manifold & airbox rubbers

All of this is very time consuming (hence the expense if someone else does it) but not overally difficult..