Author Topic: intermittent on one cylinder RD350  (Read 259 times)

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Offline craigt

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intermittent on one cylinder RD350
« on: July 23, 2021, 02:37:13 AM »
Help.. 1975 RD 350b left cylinder only firing intermttently and will not rev past 5 k. History 21k miles new piston and rings honed out 130lbs compression. pressure test small intake leak fixed holding 7lbs ten minutes. Vape power dynamo ignition/charging system 2mm before tdc.Carburetor rebuild mikuni jets including float needle and seat/choke plunger also checked float height synced slides cleaned tank... cleaned carburetors several times did not do balls out but the passage is clear.Exhaust is clear and rebuilt petcock 2 inline filters new fuel lines and oil lines. wiring vape system plugged in 3 connectors...then one black wire from relay to keyed ignition wire that went to existing coil red/white. 2 brown wires from relay to ground..1 brown wire from regulator -battery ground also ground from harness and seperate ground from frame going to battery.  red wire from regulator-positive battery splits - harness then through fuse to ignition. when the bike is running right cylinder sounds good and very hot too touch..left cylider not as hot does not sound strong also looking at plugs left side real wet right nice and tan. put strobe on it other day no spark left side removed and installed plug wire from coil then was getting spark..but then seemend to cut out again. tryed switching plug wires on cylinders ran the same but do not know if valid test. vape system fires both plug wires all the time wasted spark set up...thank you for any help

Offline adrian1024

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Re: intermittent on one cylinder RD350
« Reply #1 on: July 23, 2021, 08:41:06 AM »
In my opinion "base -iddle" position of both slides in carburettors are not the same.
If one slide is higher, and second is lower then this problems can occure.
The temperature of the cylinders will also vary. The engine will not rev up properly.
One plug will be wet and another not.

The best way to check it is to take off carburetors out from inlet rubbers with gas cable connected. Be sure that throttle cable is not twisted etc.
« Last Edit: July 23, 2021, 08:43:58 AM by adrian1024 »

Offline craigt

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Re: intermittent on one cylinder RD350
« Reply #2 on: July 23, 2021, 10:04:09 AM »
Thanks Adrian good thoughts I had synced slides and also removed throttle cables and lubricated. I can check idle screws again from what i know it was suggested run one cylinder at a time and set idle screw. With the vape Ignition if you remove plug lead you have to physically ground it out but i can just use alligator clip lead to do so. Do you think that would have effect 1/4 throttle and up?

Offline adrian1024

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Re: intermittent on one cylinder RD350
« Reply #3 on: July 24, 2021, 08:43:27 PM »
If iddle positions of slides at both carburettors are not the same it will take affect in whole range of throttle.