URGENT HELP WITH CO level

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porschekz
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URGENT HELP WITH CO level

Post by porschekz »

I've a 80' CBX with 20.000miles on the clock with VB 62 carbs imported from US .

After a full check of valve tolerances(they are in the good range) I refurbished the carbs with Randakk parts and following all (I hope) Mike Nixon carb bibble recomendations. The engine start very well and the idle range below 900 rpm is stable. It sounds excellent but.....the problem came he is so rich. The carbs have been cleaned in an ultrasonic bath and they have standard settings in the VB 62 carbs with 110 main jet and standard mufflers 6 to 2. I replaced the pilot screw, since one of the original was bended. The float level was fixed very exactly in a specific bench I build using external fuel line to adjust the level at the right level as per Dave suggestion.

I' ve checked the CO level at idle range and in both mufflers the level reach over 7,00 when the pilot are at 1 1/4 turns from closing, Since here in Spain the maximun level required on exhaust control station is not more than 4,5., I 've a significant problem.

How I can adjust the carb setting to reach this level? Does any one know what it is the original CO level with standard settings for this 80's model?.

When a tryed to reduce the CO level closing the pilot screw to less than 1 turns, the CO level still at the same level without need to readjust the idle screw. Even when I closed all pilot screw, the engine start very well and the CO level still at the same 7,0 level with an idle very stable at 900 rpm. So far if the pilot are closed it should no keep the idle ?.

Since I need to go the next week to pass the emmisions control, any suggestion should be highly appreciate.

Cheers Juan

famonteiro
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Re: URGENT HELP WITH CO level

Post by famonteiro »

Hi mate, main jets seems to be very large, mine has 92 and suports a K&N filter.
If the engine does not stop with pilot screws closed it means the idle is being feed by main jets.

They are also carbs that works reverse mode I mean riches mixture when screws are turned right, try to get a carb diagram.

fernando

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Mike Nixon
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Re: URGENT HELP WITH CO level

Post by Mike Nixon »

porschekz wrote:Does any one know what it is the original CO level with standard settings for this 80's model?.
Hi, Juan. 3 percent CO is ideal on a 70s/early 80s Honda. This corresponds nicely to 2 1/2 turns on the pilot screw on the average CBX, less (1 3/4 to 2) on CBXs that are thoroughly fettled. As for causes of richness, there could be many. Overflowing float bowls (detect this by viewing the CO swinging wildly up and down), fuel in the crankcase (test with EGA probe, engine not running of course), and partly plugged idle circuits (the engine, not getting what it needs from the strangled idle circuit will instead pull from the needle jet/jet needle).

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