E: Engine Comet Mongrel

Cyborg

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It has an Alton, so 12V no problem. In my "some day I'm going to use that" drawer, I have a similar digital voltmeter and a couple of O2 sensors. Never could get used to calling them lambda sensors. Perhaps from working with the Japanese? Easier to pronounce O2 I suppose. I just need to buy a bung. Not sure why I didn't add one to the list when I placed my order at http://www.bungking.com/o2-sensor-bung/ I saw them on there.....bought a bunch of alloy fittings for the oil & fuel tanks (thanks to Oldhaven for the link).
 

Cyborg

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I used a sniffer up the tailpipe on a local comet that was running very rich. Marked the throttle openings on the twist grip and took if for a ride, rich here, very rich here, etc.. After about three or four trips "around the block" followed by jets changes (only one at a time) we got it very close. It requires 12V to power it up. When you get the mongrel running we could try it if you want......

I tried it on the TTR but with a too long too small exh pipe and could not get a reading. I suspect that there was too much turbulence at the end on the pipe. It now has a bigger shorter pipe and goes waaaaaay better but haven't had the chance to take it to a track again for testing...

My heartfelt thanks for saying when and not if.
Must be a compact gas analyzer if you can take it with you.
 

davidd

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Make sure the sensor is in the correct location. Some want it 8" from the valve. Some have trouble being in a straight portion of the pipe as they work better on the outside or the side of a curve. Cars often place them 40" from the valve as they have lots of primary tubes.

David
 

vibrac

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Yes our comet was about 10 inches down the exhaust pipe on the side nearest the timing case it has an M8 screw bunged in it when not on the rolling road
 

eglijim

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A lambda sensor will definitely save you a lot of guesswork concerning all carb components. The sensor plus M 18x1.5 mm stainless thread and plug is easily found at Ebay, same with a little digi voltmeter as shown on the BMW damper knob, sensor under the gear box. 0.50 Volt is perfect lean, up to 0.70 V OK, above is too rich. For 6 V systems you carry a 12 V battery to supply the sensor heating, four wire type, for bikes so you can do real road tests ! You will be amazed how far from perfect a stock carb can be on a classic.

Vic
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If using this system to set up a twin, would you suggest a pair of sensors(switchable) before the pipe junction so you can check each carb individually ?.
 

oexing

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You are quite right, basically you´d need two sensors per two carbs, but it is not practical on the Vincent when you like to hide the permanent M 18x1.5 weld-in thread. Best place seems to be in the ex pipe just before it enters the silencer, in horizontal orientation - I guess. You will choose the heated four wire sensor type as on a single or twin there is not enough heat at that distance from the cylinder. I´d get new needle jets and needles anyway as these components can wear and when doing road tests you change any components in both carbs with same sizes of course. That should be close enough even when having only one sensor per two carbs like with the BMW setup.
These exhaust sniffers, are they the CO or CO2 testers ? You would not find them at small costs with battery power and small sizes to be used for bike road tests ? The O2 sensor plus voltmeter is only around € 30.- so no big deal to have it on the bike for some time. I am still busy with a Bing carb configuration on one Horex 460 , no spares for that type of Bing so this will go on for a while tweaking carb components for smooth operation at all conditions.

Vic
 

Chris Launders

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I like the idea of fitting Lambda sensors as I'm rubbish at setting carbs up properly, I've two twins and I'm sure I can get hold of some old pipes so could mount two sensors part way down before the pipes join and swap back to the "good" pipes once I've got the carbs sorted
Has anyone any recommendations as to what sensors I would need so I could get everything made and set up over winter ready to fit.
Chris.
 

Chris Launders

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That's an awful lot more money and complexity than I think I need or am prepared to spend, I don't need any recording or data-logging, Lambda sensors on ebay are £10 upwards and digital voltmeters are about £4, I'm just not sure which Lambda sensors would be usable.
I've got twin 5" clocks so two small voltmeters can be mounted there virtually in line of sight and I have the twistgrip already marked at closed, 1/8th, 1/4, 3/4 and full throttle.
So all I would need to do is ride at a previously decided steady throttle opening up a steady gradient and glance at the voltmeters surely.
Chris.
 

oexing

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Chris, the four wire types are best on a motor bike as down at the far end of the exhaust pipes temps are too low without heating. Two wires for heating from 12 V plus two wires for the voltmeter. The operating range of these sensors is narrow, you want 0.50 - 0.70 V with a good carb setup, below 0.50 is a bit lean and above 0.70 it is getting rich. I would only fit one sensor, you change carb components with same sizes on both carbs at a time - good enough. The ss M 18x1.5 mm thread can be welded easily without showing from the outside, oriented horizontal pointing to the clutch, permanent, no blueing of the chrome to see with TIG welding.

Vic
 
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