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carb synch

ffjoe
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ffjoe

ffjoe

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I want to hook up a dwell-tach meter that I have from the old days when you could work on a car to my 2nd gen to set the idle speed. There's two wires on it and I think one went to ground and the other to the coil. Anyone know where to hook up to get a reading for tach?

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bkuhr

bkuhr

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Old dwell/tach meters were designed to be hooked up to vehicles running points type ignition. They typically attached to the minus side of the coil (the points side of the coil).

Depending on the impedence (internal resistance) of your tach/dwell meter, you could do damage to your electronic type ignition. If you continue along this persuit, you will need to hook up somewhere on the negative side of coil, where other side of coil has battery plus. Not sure how 2nd gen made, but could find this wire in/at your ignition box. Would not matter which peticular coil you attached to. On first gen, this coil wire (#2 coil) also feeds the dash tach, and could be accessed at rear of dash.

 

Recommended option IMO would be to get one of the new digital tachs where a lead wire just wraps around a coil wire.

 

FWIT:2cents:

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V7Goose

V7Goose

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I want to hook up a dwell-tach meter that I have from the old days when you could work on a car to my 2nd gen to set the idle speed. There's two wires on it and I think one went to ground and the other to the coil. Anyone know where to hook up to get a reading for tach?

Your old meter should work just fine, but if you expect it to read the correct RPM it will need a setting for a two-cylinder engine (we have four separate coils, but each one has a waste spark like a stock HD dual-fire ignition, so it fires one time on each revolution of the engine). I use an old RAC tach/dwell meter in my shop all the time, and it has worked perfectly on every RSV except one where it showed a strange bounce.

 

The tach trigger wire needs to be connected to the side of any coil that does NOT have the red/black wire on it (each coil has +12V red/black wire on one terminal and a different color on the other terminal. If you do not want to remove the tank, you can access the terminals on the rear coils from under the bike near the swing arm, but that is a bit of a pain. If you are not going to mount a permanent coil on the bike, I recommend you remove the tank and attach a single wire to the top terminal of the coil mounted on the right side of the frame backbone and route it up along the tank vent hose to terminate under the plastic key cover on top of the tank. Use a small zip tie to hold the end of the wire against the end of the vent hose so it never gets lost. Then all you need to do to attach your shop tach any time you need it is to simply remove that plastic cover.

Goose

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N3FOL

N3FOL

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I just read some reviews on this tool and most said it didn't work well. Any other suggestions.

 

I am not sure how other people are using the tool, but I've never had any problems using it on my Venture everytime I check and adjust my idle.

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  • 2 weeks later...
V7Goose

V7Goose

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I just synced my carbs with the new dial gauges I just bought. The dials bounce a lot when the engine is running. So what I looked for is where the dial peaked and set them to the peak. I hope that's correct.

Your gauges came with four valves to put in-line with the gauges. You adjust the valves to calm the pulses so that the gauge just wiggles, this makes it much easier to compare the readings between cylinders.

Goose

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uechi kid

uechi kid

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Your gauges came with four valves to put in-line with the gauges. You adjust the valves to calm the pulses so that the gauge just wiggles, this makes it much easier to compare the readings between cylinders.

Goose

Ah ha. So that's what those are for. When you adjust the gauge to just a wiggle I'm assuming it doesn't change the needles position (value).

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V7Goose

V7Goose

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Ah ha. So that's what those are for. When you adjust the gauge to just a wiggle I'm assuming it doesn't change the needles position (value).

As long as there is some wiggle in the needles you will be seeing a good vacuum reading. When the needle bounces, the highest reading is actually the true vacuum during the intake stroke, but the vacuum bleeds off while the intake valve is closed during the compression and exhaust strokes. By using an inline restrictor to the vacuum gauge, you basically allow the gauge to hold onto most of that vacuum before the next big pulse. You want to see a little wiggle in the needles so that you know you have not closed the restrictor valve too far.

 

When you synch the carbs, the actual vacuum reading is not near as important as all carbs reading the same value. I cannot remember for sure what the spec is for vacuum at idle, but I think it is about 12" Hg. Not all of these bikes will show that, but anything over 10" is typical. If you see a bike that is less than 10" at idle, it is a very strong indication that the pilot jets are plugged or the mixture screws are way too far in. When the engine cannot get enough fuel through the pilot jets, the idle screw needs to be turned more to open the slides and allow the fuel needed for idle to come through the main jets, and this will significantly drop the idle vacuum reading.

 

If the synch changes when you rev the engine, then you may have either just one or two pilot jets partially plugged, or your sync is just not quite right. USUALLY I can get a bike to hold the same sync at 3,000 RPM as it does at 1,000 if I keep fiddling with it (redoing each sync step with extreme care), but once in a while it just won't dial in. In those cases, carb cleaning is indicated.

Goose

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