hi guys looking for help with my 1985 43f 600 , i posted a few weeks ago about resister plug caps . my 43f is running better but still does not start consistantly good like it used to . another problem is at 4000 rpm plus the power surges it used to sometimes do this but it was more of a flat spot and would rev through it no problem , also when i deselarate to change up the gears sometimes there is a small pop through the exhoust , now i am 90% sure this is all carbareter problems but 10% thinks i have a ignition problem hence my consern over resister plug caps . could a bad cdi do this , ive dissmantled the ignition switch and cleaned it and there seemed no problem there just oily gunge in it , so thoughts please guys this is the first problem since i bought it so reliability has never been a problem up to now . thanks zigzag

This is just a trouble shooting measure. To make sure you don't have issues with corroded or shorting kill functions, disconnect the Black/white strip wire from the CDI under the tank. This will remove external kill functions completely. If you still have the exact same symptoms then this is NOT your problem, hook it back up.

The small backfire on deceleration is usually a lean mixture. Could be clogged jets or passages, could be the decel enrichner circuit is not working. The left carb has a round cover plate on the side of the carb. This houses a diaphragm that when activated causes a richer mixture on decel. The hose that routes over the secondary carb brings the vacuum from the intake of the cylinder that operates the decal valve diaphragm. Make sure the hose is NOT leaking. It would be a good idea to just replace the vacuum diaphragm and brass valve. These are available from Yamaha. Use only OEM parts for best results.

Adjust the fuel screw at the bottom of the primary carb at the front (cylinder side) using a small flat blade screwdriver. Adjust it for a peak iidle RPM. This sets the mixture. Starting place is 1 1/2 turns out. Since this is a fuel screw, inward is leaner, outward is richer. When done readjust your idle speed. This is good to fine tune if you change to a very different altitude. At 1200' amsl mine is set at about 1.5 turns out, at 12000 feet amsl last year in Colorado I set it at about 1/2 turn. It ran fine. When returning back home bike would not start until I remembered to screw the fuel screw back to 1.5 turns out. The started normally.

Pull you plug, hook up to spark wire to plug, ground plug. Kick hard, you should see a bright blue spark, it is red or spindly then it is weak. Could be the CDI or Coil.

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'84 XT600 is now bored to 2nd oversize and new OEM pistons and rings installed. No more smoking.

hi and thanks steveloomis i will try disconecting the black white wire at the week end , ive looked at the coasting enricher diaframe tonight it seems good the plunger is free but the housing/compartment was oily /dirty so have cleaned it all out and put it back together , so will see what it is like going to work tomorrow . zigzag

I don't own a Yamaha 600 but do own a KLR 650. My bike started showing exactly the same symptom as yours about a year ago. I've spent a year stripping carbs, cleaning connectors and the like with the problems slowly getting worse. Finally a few weeks ago the bike refused to run - solution has eventually turned out to be a new CDI unit . With this fitted the bike suddenly runs hke new . Wish I'd bitten the bullet and spent the money on it Months ago.

Sent from my SM-P350 using Tapatalk

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Martin

finally back on the road again


http://awayonmybike.blogspot.com/

I can echo that, my 86 XT that I purchased new got to be hard to start, ran poorly, back fired quite a bit. It was leaking oil all over the place so I started by removing the rocker box and resealing. I replaced all the rubber parts, cleaned the carbs throughly, replaced the seals in the carb slide lifter shaft plus gaskets and decal valve diaphragm. This process was all through the winter. When done I rolled it out and it refused to start, no spark at all. I pulled the cdi from my 84 that I purchased as a parts bike and it had no spark.

I then set down with the manual, OEM is best, and tested the ohms of the stator coils, ignition coil wires, grounding circuits etc. I used the AC volt setting on my volt meter and measured the trigger coils for output, they did have a kick when kicking over the engine, I checked the cdi charging coils for a kick and they did. I then compared all readings to the 84 and got very similar readings. I concluded it must be the CDI.

I knew I did not want to buy a used one that was probably old as the two I have so I ordered two of them from the guy in New Zealand. I waited and waited with no response and got to checking elsewhere.

I contacted Zeeltronic as I already had good experience with their CDI's on my Yamaha two strokes. Borut said he did not have a CDI for the XT but would look into it. He then made me one to try out. I think I got it just a short time after the New Zealand units showed up.

The Hyperpak unit was installed and the bike started right after a few quick kicks, idled perfectly.

When the Zeeltronic unit showed up I programmed it with a few small changes from stock, they do come ready to use but since I was already familiar and had the necessary programing cables and used the provide software I altered things a bit.

The Zeeltronic unit SEEMS to have more low end punch, I even swapped out the units after warming the bike and A B compared them back and forth. I still think the Zeeltronic has a bit more low end. Some have agreed with me some not.

So to end this long version story. These bike are getting some age on them and CDI's do age and fail.

Steve

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'84 XT600 is now bored to 2nd oversize and new OEM pistons and rings installed. No more smoking.

hi guys and thanks for your replys , last friday i took the carb off the bike and cleaned the outside then stripped it down and put it in a friends ultrasonic cleaner i borrowed . the whole carb would not fit in and submurge so i had to keep revolving it around , 2 hours later and i reasembled it . i removed the intake rubbers and resealed them, then on with the carb . the bike started 3rd kick and runs well , i will post again in a few days to report back how things are going but it is starting ok, will have to take it for longer run to see if it still surges in the higher revs . it still pops a little on slow speed up changes ive reset the mixture screw to 2.5 turns out which i think is correct, before it was 3.5 turns out so it is now a little leaner . zigzag

hi guys the problem has returned big time , i set of last night 5 o clock called for petrol all was well , called at mates house only few minites took 4 kicks to start , 2 miles in to ride on strieght road doing 30/40 mph bike dies starts then dies completly . tryed for 5 mins to start only got nothing then a spit out of the exhourst then dead . called a mate with a van to rescue me. at home no spark , diconneced black/white wire from cdi (thanks steveloomis) got weak spark hooked it back up no spark disconeced kill switch wirers weak spark hooked them back up still weak spark ? . tryed for two hours no spark/weak spark. up at 10am cleaning connecters weak spark no spark sometimes nice blue spark, but no run . after cleaning carb last week bike pulled good and strong i now think this was dirt in the carb and not related to bad starting i was having . still removed carb to check/ blow through with air line . started to check connections under tank there was a 4 way black crimped joint seemed iffy so made new connection with good bullet connecters tryed to start bike, 4 kicks it ran but would only idle/ tick over any revs and it started to die put timing light on to see if i could see misfire but very hard to see bike ran 2/3 min then died did this 3 times on idle sounds perfect , changed a few more connecters no run and very weak yellowish spark , tested coil on workshop coil tester all good have i got a bad cdi or still a bad connection ? can get cdi £100 ish from wemoto anone had 1 any good

hi guys a bit more info the bike is a xt600 49r american inport the cdi has 11 wires 2 of the wires are red and brown but thay do not connect red to red etc , they connect red to brown and brown to red they have always been like that 18000 miles ive done on the bike i tryed putting them right way round but loose spark completly ? just checked and a company in belgium does a 49r cdi but they are on holiday until the 23rd august . ive dealt with them before and they are first rate very fast delivery etc . so if i have to get a new cdi do i go red to red or red to brown zigzag