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· zborschuk
112 Posts
Discussion Starter · #1 ·
I recently used a CarbMate to sync my throttle body because the idle speed would vary about 80-100rpms, but often up to 140rpms. I managed to get that down to 20-40 on average with the occasional 50rpm jump when reading from my laptop connected to the PCIII. The bike is an 02 1800R with 34k miles on it. Out of curiosity, I brought the engine speed up to about 3000 rpms with the CarbMate attached to see if it was still synced at higher rpms. It isn't. It flickers between -2 and -3 on the readout at that engine speed. Did I sync the throttle body incorrectly? Or is this indicative of another problem? What could cause this if it's not normal? Any help would be greatly appreciated. Thanks!

· Registered
4,945 Posts
That is a good question. In all the time I've had my 1800 I've not seen where anyone , including myself, has had to sync the throttle body. So I'll be watching this one pretty closely.

· Pursuing Perfection
5,866 Posts
Not sure I understand what you mean.
There's two butterflies -
They can be altered - if one is more seated than the other - that's a problem.

Simply adjusting fuel - at PCIII, vs throttle body mechanical, not seeing the relation.

· Pursuing Perfection
5,866 Posts
When the idle vacuum is equal the bike will have a smoother idle
and it helps cut down on decel popping when slowing down with the throttle completely closed

That's All Sync is for - closed throttle.

The CarbMat is the vacuum sensors being used to see the air gap of butterfly.

So in answer to original question-
Measured vacuum at Throttle stop only.
Nothing above idle matters.

If throttle was opened suddenly - meter should drop to basically zero.

By all rights -
simple vac gauge should be used by those who inherently lug their engines.
It would prove the point in real time - always adding more throttle in too tall a gear.
Too lazy to down shift.
Over pounding the pistons to crank bearings.

Same with aircraft and constant speed prop.
The pilot doing the same lug tactic - would loose the engine in flight not keeping the vac manifold pressure in check.

There's plenty of pilots here to verify.

· Pursuing Perfection
5,866 Posts
Never used a Carbmate -

The LED's spread on face looks a little deceiving -
I'd have to see live video - Youtube maybe has it.

Using Vac gauges - I want to see hair line difference.
Not some phantom gap between 2 lights - what ever that spread is between two.

After watching a video sample - looks like tool can fine tune sensitivity range.
I'd probably link in vac gauge just to be happy.

I can see where setting engine speed higher may look off.
Most video's so far are cable operated twin carbs - a little more sync problems involved.

The one demo so far - the guy wastes too much time with blah blah blah,
and isn't quite up to speed - so I won't link it. 7 out of 10 min wasted.

With dual carbs/cables - It requires a pre bench sync of the slides first,
so they both move off bottom of port at the same time. Lubed perfect as well.

Not doing that first - would make one throttle making increase in rpm,
before the other even started to move yet.

Adjusting cables/slides first & balance afterwards for clean idle.

Ours - single shaft for both plates at same - much more precise.

But this guy at least knows what he's saying if you want a little OJT on carb sync.
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