Carb tune at home?

[Tat2demon]

I'm sure this has been asked many times before so I apologize, but either I cant find the answer or I'm just not bright enough to understand it.

Next week Ill be getting a set of carbs from DiverRay.

As I understand it, after doing anything to carbs they need to be tuned.

From what Ive gathered, they can be tuned at idle without anything really special, but will also need to be tuned for the high end at load? Am I understanding correctly that this needs to be done in a shop?

I called around the other day to find a shop that would do them. One wont touch anything more than 20 years old, another says they cant take any more bikes until after Sturgis, and the third says they can do it but it will be around $200.

I would hate to pay that much for something if its possible for me to do it myself. I know Ill need to do it again in the future for the new exhaust and again for the complete bike rebuild this winter.

Any input would be greatly appreciated.

[James England]

The carbs need to be cleaned thoroughly and blasted out with compressed air (float bowls off). You need to remove all the jets etc and clean everything thoroughly (if it hasn't been done already?).

Re 'tuning'.... synchronising the throttle butterflies is the main thing. You can do it on the bench visually (using paperclips under the butterflies) or, as I did, just by eye. But.... you will have to use vacuum gauges to get it right. These are available on eBay for about $50 or less. I bought a cheap set and they work absolutely fine. I did my XS1100 and my Goldwing with them. They are a one-off purchase and well worth it. You're going to need them.

The other thing is to ensure that the mixture screws are all a similar number of turns out and that the plugs are a nice tan brown.

Also, you may need to adjust the throttle stop screw on the bank of carbs once you get the engine running. If it's ticking over more than 1000rpm, then unscrew the throttle stop. Or the reverse if you can't get it to run without the throttle being twisted....

[BA80]

Nate, you really can't trust a bike tech that's younger than the macine he's working on anyway.

These bikes really aren't all that difficult to tune if your mechanically inclined at all.

Many have spent big $ on fancy tuning tools but IMHO all you really need is a basic set of sync guages and the seat of your pants.

The carbtune guages with the steel rods is expensive and not very accurate in my experience.

You can get a set of plain jane carb syncronizing guages for about $80 and they are easy to calibrate and check.

Heres the exact set I have for $64.50 http://www.amazon.com/Carburetor-Syn.../dp/B004MSJ7E6

As far as tuning to carry a load you'll just need to ride it under the conditions you want it to work best at and check your plugs and see how they look to see if you need jetting changes. Sorry, there ain't an easier way these bikes are old school.

[Tat2demon]

I guess I was really worried over nothing. I thought it was a much more involved process. Do you guys recommend buying gauges over the DIY one I saw in a post around here?

Thanks a lot guys.

[BA80]

are a one-off purchase and well worth it. You're going to need them.

The other thing is to ensure that the mixture screws are all a similar number of turns out and that the plugs are a nice tan brown.

This is true to start but there a 4 DIFFERENT cylinders and 4 DIFFERENT carbs running under 4 DIFFERENT conditions so the IDLE mixture screws could be all different when you are done tuning. In a perfect world you might have 4 cylinders running exactly the same but it's highly unlikely.

The plug color is what I was talking about when I said "check your plugs". This is where you'll see how it's running above idle under the conditions you ride. James is correct with the tan/brown color. It needs to be ridden a bit to get a good plug reading though

[Tat2demon]

To do that do I need several sets of plugs? Ride, check the color, pop in a new set, rinse and repeat?

[BA80]

To do that do I need several sets of plugs? Ride, check the color, pop in a new set, rinse and repeat?

Not necessarily. Under combustion conditions they will change with conditions fairly easily.

It may be easier with a couple sets though.

My advice ALWAYS is to start with all stock components and get the bike running as good as it can that way and adjust from there. 9 times out of 10 stock rocks.

[Tat2demon]

As far as I can tell, once I get this new set of carbs, everything will be stock again. The only mechanical changes I plan on is new exhaust. Other than that it will just be cosmetic changes for now.

Do you recommend using a Colortune or can I get by without it by just checking the plugs?

[CaptonZap]

I don't know if things have changed in 20 years, but the color tune that I have says that the plug is NOT to be run at much above an idle.
Which is probably said to keep some one from blowing it apart at speed.
Not to mention the fact that it would be hard to check the color while riding down the road. If you get one, that will be easily understood when you look at it.
Plug reading is the way to go for 1/4 to full throttle tuning.
I think I've used mine twice in twenty years, so if you are not flush with fun money, save it for some vac gauges, you can do just as good with them. CZ

[Tat2demon]

Sounds good. Thanks again guys. I feel much better now.

[crazy steve]

Do you guys recommend buying gauges over the DIY one I saw in a post around here?

That DIY would be this one: http://www.xs11.com/forum/showthread.php?t=986
.. and these set-ups work just fine. It's what I use, and I wouldn't spend the money for anything fancier... but that's me

[Tat2demon]

Well if that works that's what I'm going to use. I'm a very DIY type of person. Not so much because of the money savings but it makes me feel good when it actually works.

[James England]

I mean, as a starting point, of course. Set the mixture screws same number of turns to start with and adjust from there. Better than starting the process with the mixture screws set at different number of turns. When correctly adjusted, there shouldn't be much more than 1/2 turn difference anyway...

This is true to start but there a 4 DIFFERENT cylinders and 4 DIFFERENT carbs running under 4 DIFFERENT conditions so the IDLE mixture screws could be all different when you are done tuning. In a perfect world you might have 4 cylinders running exactly the same but it's highly unlikely.

The plug color is what I was talking about when I said "check your plugs". This is where you'll see how it's running above idle under the conditions you ride. James is correct with the tan/brown color. It needs to be ridden a bit to get a good plug reading though

[JerseyJon]

The voice of the non-guru

Hey Nate,

I was in the same boat as you. I needed to tune up my carbs because the bike was running like crap and one cylinder wasn't firing. I didn't have the time to clean the carbs all on my own, so I'll do that this winter. However, I did the sync myself. Like an idiot I ended up doing all three sync guage candidates. The first one was the motion pro blue fluid tool. That doesn't work very well. The fluid is not heavy enough, so it's very easy to suck it up right into the engine. also, calibrating it takes longer than syncing the bike. So then I tried the pet store/fish tank/ homemade version. That was ok, and fun to make, but it's a lot of shopping, and even with the convenience of the fish tank manifold, it takees time getting the pairs of cylinders to the same vacuum levels. I'm sure these guys here can do it easily, but they've had a lot of practice, and in the meantime, your bike is overheating in your garage. I ended up buying the 4 vacuum gauge tool for about $65. It's from Hong Kong I think, or China, so it takes a little while to get there. But it makes the process phenomenally simple. you see the gauges clearly all at the same time. You can get a feel for the screws and the throttle and how they affect the needles on the gauges. It will all go very smoothly, I can assure you.

The bottom line is that I'm pretty new at this, and I've tried all three. If you can part with $65, order the four vacuum gauge setup, not the fluid one, nor the homemade fishtank one.

[fredintoon]

I guess I was really worried over nothing. I thought it was a much more involved process. Do you guys recommend buying gauges over the DIY one I saw in a post around here?

Hi Nate,
"The truth will set you free, but first it will make you miserable"
The simplest DIY gauge is also the most accurate. It's also about 4 feet tall and needs to be kept upright.
Take four 12-foot lengths of aquarium tube sized to fit on the carb manifold vacuum connections and join them all at one end.
This needs a crosspiece but they are hard to find so use two Tees joined to make an H.
Pour the tubes about a foot deep with ATF, the red color shows well and it won't hurt the motor if it happens to get sucked in there.
Tape the fourplex to a yardstick to keep it tidy.
Put the four tubes on the four vacuum taps to do the balance.