Synching Carbs
I need to synchronize the carbs on my GS1000. I don't have the vacuum test set, so I was wondering if anyone's done it by measuring the EGT (exhaust gas temp) of each cylinder. To do this would you recommend going Lean of Peak temp or Rich of Peak temp? I have tuned air-cooled aircraft engines in s symilar manner, and I was thinking that Rich of Peak would help with cooling while idling as it does with aircraft. I think this is doable, but if it would be better to just get a vacuum set and do it that way, what figures do I set the carbs to? Thanks for the input.
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Go to lean and you run the rick of burnt valve or piston. I always use a 4 bank vacuum tester. 0 -
I'm thinking I can get a good tune by going off the temp of the header pipes, just balance them across the board so they're all running at about the same temp. 0 -
Do it with mercury sticks. If you can't borrow some, let a bike shop do it. I've seen too many good engines get one cylinder burnt from being too lean and ruin the whole engine.[;)] 0 -
Could just use this as an excuse to buy more tools. 0 -
Spend the $ on renting/buying a synchronometer and do it right. 0 -
A cousin of mine has a vac gauge set, I'll do both see how it works out. I think it can be done the way I described. 0 -
I have to add, I have the proper equipment to accurately measure the temp of each header pipe, the measurements won't be guess work. 0 -
The best $25 I EVER spent [mid-ninties] on a motorcycle.
My '81 900 Custom was absolutely fantastic after that last bit of the tune-up.
I later tried a 900F with the same [complete, though all dealer] tune-up.
It makes a WORLD of difference in throttle response and engine performance.0 -
The theory ought to be the same for motorcycles as for automobiles, and for cars there are, or at least used to be gadgets available called variations of the word synchronizer. My dad had an XK-E 4.2 Hi-Comp that had 3 2V carbs on it, and it was always trying to see how rough three groups of two pistons could do; he got a Syn Chron izer or some such, and that really smoothed things out. 0 -
Do NOT go to lean. Lean is the basic cause of pistons getting burn through. ( melting a hole through the top of the piston.
Go to a shop and have it done right. Nothing like peace of mind when your a 100 miles from home.0 -
Mercury sync sticks are much better than gauges. They cannot go out of calibration. Vacuum sync the carbs first. In leu of an exhaust gas analyzer, use the idle drop method for setting mixture. With a sensitive tachometer connected, turn each mixture screw(engine side, start with all four at 2 1/2 turns) in until you see a slight drop in idle. Then turn it out til it picks back up. Go through all four twice. I usually add 1/4 turn to all four after this. If your bike has air screws(some early GS's had both) set them all at 3/4-1 turn. Air screws will be on the airbox end of the carb. Before you do any of this, make sure your points are set properly. 0 -
quote:Originally posted by catpealer111
I'm thinking I can get a good tune by going off the temp of the header pipes, just balance them across the board so they're all running at about the same temp.
You are very correct on your assumption. This is how go kart racers tune their carbs while racing. However, as said before, go too lean and you will make the engine too hot. Go kart engines preform at a much higher rpm then your engine and they also run a lot hotter. My guess would be for motorcycle racing, they use the EGT to tune their carbs, its the most accurate way to do it. What you need to do is find some racing information for motorcyles and a gage. In go kart racing, there are headers to attach the EGT sensor, or you can make your own. The two most common gages in racing are Mycron and Digitron. Used Digitrons are selling cheap right now because the Mycrons are just that much better. The next problem would be knowing what temp to set it at, this would be specific for the engine.0 -
Is that the same setup that is used to set the old Honda four cylinder bikes from the 1970's. A vacuum gauge hooked to a alum block which has four ports that attach via small hoses to a port in each carb or the intake area. You just switch the flow from one to the next to set each carb. My gauge has four screw in adaptors that screw into each port to allow attachment of the hoses to the gauge. The size of the adaptors might be an old Honda standard size.
I have one of those from the 1970's. Would that work to set your carbs? What year is the bike?
Here is a picture of my setup.
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I read an article years ago about the best way to set up multiple carbs. The EGA (exhaust gas analyzer) that is used for emissions testing is the key. You need a tap for each exhaust port which may in itself be a project but the results are supposedly so sweet that there is no comparison to vacuum method.
I would have done this with my GS850G but I sold out and went to fuel injection by buying a Vic.
EGAs can be had on Fleabay for under $100.
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On Formula racecars, I use the lean egt.
But they only have to run 45 laps.
Safest & cheapest way for you would a manometer set, to set the base line, then minimal lean up on the egt's to around 1300-1350.
Dont go higer than 1350 cause your on the edge right there.
Good link on EGT tuning
http://www.rodmachado.com/Articles/Article%20of%20Month/Articles-of-Month/EGT/EGT-Primer.htm0
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