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Author Topic: Syncing Carbs and General Tuning  (Read 771 times)

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Offline welovedon

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Syncing Carbs and General Tuning
« on: April 10, 2013, 10:31:42 AM »
Hey guys,

So I wanted to see if there was any technique for tuning and syncing my carbs with out using a dynamic sync.  Also how do i adjust the amount of oil the injector shoots into my carbs? 

I'm running a K&N single air filter into the two carbs and DG pipes.  What should my bike be tuned to?  I'm also in Southern California about 15 miles from the ocean. 


Thanks guys.

Offline clem79

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Re: Syncing Carbs and General Tuning
« Reply #1 on: April 10, 2013, 10:47:12 AM »
On the syncing, you can do it without the bike running by pulling the air filter and y boot off and mechancially making sure they start moving at the same time and are wide open at the same time.  There is a procedure for it in most tuning manual, the one I am thinking of is the Sudco mikuni handbook.  Well worth the money for a tuner.

Adjusting the oil on a RD(might be the same for a DS7/R5, not sure)- Adjust the oil injection cable as it goes in to the right side engine cover(exactly like you would adjust the carb sync).  Why are you wanting to do this?

On the jetting, what size is your bike?  What year is it?  Any internal engine mods?  Have you rebuilt the engine?  If so, new bore?  New crank seals?  Stock carbs? 

I would throw some numbers out there, but I am at 5000 feet.  Whatever you do, don't take other peoples numbers as an absolute have to run.  Every bike is different, there numbers will get you close but in the end you need to give the bike what it's asking for.

-Adam
« Last Edit: April 10, 2013, 10:49:42 AM by clem79 »
1972 R5C w/ RD350 top end
1975 RD250- The lifelong project

Offline welovedon

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Re: Syncing Carbs and General Tuning
« Reply #2 on: April 10, 2013, 03:34:48 PM »
my bike is a '74 Rd350.  14k miles and the motor is stock.  I do need to change out the kicker seal; oil leaks out of there when im riding and it's spraying onto my pipe. 

As for the oil injector, I just wanted to know how to adjust, for knowledge sake. 

Offline m in sc

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Re: Syncing Carbs and General Tuning
« Reply #3 on: April 10, 2013, 04:21:43 PM »
There a shim at the end of the shaft. Usually its just fine as is. The bump on the cable pulley is supposed to line up w the pin when the carb slides just start to lift. There's actually a volume spec somewhere out there..........
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Offline p51bombay

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Re: Syncing Carbs and General Tuning
« Reply #4 on: April 10, 2013, 08:13:46 PM »

Offline MckayMotoWorks

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Re: Syncing Carbs and General Tuning
« Reply #5 on: April 10, 2013, 09:29:30 PM »
I have never heard of nor seen the water hose technique. Interesting
Assuming with the wave a two stroke this can't be done as intended?
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Offline welovedon

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Re: Syncing Carbs and General Tuning
« Reply #6 on: April 11, 2013, 12:20:26 AM »
Bingo!  Adjusting the screw atop the carb cover did the trick. Both carbs are now synced. But now a new issue...

When I gun it wide open, she pulls but hen she hits 7/8k rpm, she starts to jerk back and forth a little bit. Not really bogging down, but more of a should I go or should I slow down feeling.

Jets are at 220, both carbs have been cleaned.

Any ideas?

Offline pdxjim

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Re: Syncing Carbs and General Tuning
« Reply #7 on: April 11, 2013, 12:50:25 AM »
Upside down handlebars  :suicide:

Offline clem79

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Re: Syncing Carbs and General Tuning
« Reply #8 on: April 11, 2013, 11:19:33 AM »
Bingo!  Adjusting the screw atop the carb cover did the trick. Both carbs are now synced. But now a new issue...

When I gun it wide open, she pulls but hen she hits 7/8k rpm, she starts to jerk back and forth a little bit. Not really bogging down, but more of a should I go or should I slow down feeling.

Jets are at 220, both carbs have been cleaned.

Any ideas?

While riding it where it's "jerking", in a safe straight line with no traffic, reach down and turn the choke on. If it helps it, you're too lean.  If it makes it worse, you're too rich.

If you don't feel comfortable doing this, move the needles one way or the other and ride it again.  If one of these fixes your issue, then you know which way you need to go with the fuel.

-Adam
1972 R5C w/ RD350 top end
1975 RD250- The lifelong project

Offline welovedon

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Re: Syncing Carbs and General Tuning
« Reply #9 on: April 17, 2013, 12:25:30 AM »
Still having issues with the tuning. 

When riding, it will rev up smothly till about 7k rpm and it suddenly it will drop in power.  If i open up the throttle more, it goes away.  I've checked the spark plugs and they are a good brown color, the carbs are synced,  gas is flowing, 220 jets, the pin is set mid way up in the carbs.  She idles just fine and revs up fine as well.  I've also checked the compression and im looking at 120psi for the left and 115psi for the right. 

What's my issue?  Any clues? 

Oh im also running the Iridium plugs. 

Offline clem79

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Re: Syncing Carbs and General Tuning
« Reply #10 on: April 17, 2013, 10:42:16 AM »
A simple check, increase your mains one size, try it.  If it's worse, then you know the 220's were too rich.  If it's better, then you know you were too lean.  It's hard for anyone to tune a bike over a forum, don't be afraid to try things.  If you're unsure which way to go, always add more fuel.  The bike will tell you if it was the right move or not.

One more thing, where is your timing set at?

-Adam
1972 R5C w/ RD350 top end
1975 RD250- The lifelong project

Offline welovedon

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Re: Syncing Carbs and General Tuning
« Reply #11 on: April 17, 2013, 12:29:30 PM »
my timing...that part I am unsure of.  Stock?

Offline clem79

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Re: Syncing Carbs and General Tuning
« Reply #12 on: April 17, 2013, 01:31:38 PM »
my timing...that part I am unsure of.  Stock?

Ok, before you ride this bike again...  Set your timing, and set your point gap.  THEN, and only then can you start to fine tune the carbs.  Think about what the ignition timing does, it's just as important as carburation. 

-Adam

1972 R5C w/ RD350 top end
1975 RD250- The lifelong project

Offline MarkT

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Re: Syncing Carbs and General Tuning
« Reply #13 on: April 17, 2013, 03:06:51 PM »
Pay careful attention to the throttle opening when the problem occurs... 

In your first post you said "when you gun it wide open" you had a problem and then later you said "If I open the throttle more it goes away"

Two different problems? 

Basic checks such as ignition timing, air leaks, compression, etc are always a good idea before messing with the jetting.  To know what to change in the carb you primarily need to know where the throttle is held (the rpm is secondary) when it acts up.  You could change main jets all day and not really fix the issue if the problem is in the pilot or needle jet circuits.

1963 Yamaha YG1-T - stock
1965 Yamaha MG1-T - stock
1972 Yamaha R5 - frankenstein project bike
1979 DT175