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Won't rev?

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Hi,

Went to start my gas gas txt pro 2014 today and it will idle very slowly but will not rev? any sort of throttle and it just fouls the plug and pops back through the exhaust, no rise in revs. All I did was wash it, oil the chain and give it a coat of wd40 then put it away. I have cleaned the carb checked the stator side for water ingress and tried a new plug, nothing makes any difference. It idles really slow and seems to be missing a firing signal eg fires, misses one, fires again etc. The only thing I can find that alarms me is the sealant around the cdi box is showing a gap. I'm wondering if water has got in. It's perfectly dry now though, the damage may be done?  Any body else had a similar symptom? 

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I have not experienced what you describe, but I've learned to try the simple and easy "fixes" first. Have you drained the the tank and carb and utilized fresh fuel? Have you verified that the air intake and box isn't somehow blocked and that the air filter is clean and flowing? And nothing blocking the exhaust outlet?

Edited by d2w

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If water gets into the electronics, all is not lost, as long as it was clean water.   Clean water will evaporate leaving no residue, unlike dirty water that will leave a conducing coat of dirt.

So if the circuits have got wet, you need to place them in a dry warm spot for several days, a week maybe.    I once dropped a Sony radio into a bath, the only component that I could not dry was the tuning capacitor, that I renewed for £3.

.

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Typically a blocked main jet. Is it a Keihin or DelOrto? When you say you cleaned the carb are we talking full disassemble and blow out of all jets and holes? One thing that is common on the Keihin is putting the little brass needle guide/jet thingy in upside down. Done that before. The beveled edge goes up😁. Will behave as described. If there is water in the CDI it may not be dry inside even if it looks dry outside. Might take a few days extra for the water to evaporate. 

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check  your ground, I helped a guy get his Sherco running the day after he washed it.

He rode it for practice, washed it, and the next day at the event it wouldn't run.

Cleaned the ground attachment at the frame and all was right again.

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Took the flywheel off first as it was easy and I had a puller. All clean so I got the airline in and blew the dust out. The stator was like new with no blistering or discolouring. I then made an "attachment" and wound a few revs on with the drill. I got 32 volts from one leg and 14.5 from the other. I also checked the pickup and got 92 ohms which flicked to 40 ohms at the trigger point. I next checked the voltage regulator and got  12+ from the lighting plug and the same from the fan plug with the thermostat by passed. I have cleaned the carb through with the air line and using the small red pipe on the gt85 can, all good. I did tip the bike on it's end to see if there was anything in the exhaust but I'm quite careful when cleaning and nothing came out. I managed to ease the cdi apart but as the green block came out with the plug it was dry and the block is sealed, it looks like a lump of candle wax. I can see no way of water getting in there. I'm kind of convinced now the cdi has died, very weird that it packed in the very second I stopped it though? While I was riding it there was no sign of anything wrong!  

Cheers for all the ideas folks.

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Sorry to hear no success. Make sure to let us know when you do get it sorted. Knowledge shared is knowledge multiplied. 

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Maybe no use at all, but I had a similar issue on my 18 last year, just decided to run badly, intermittent start but wouldn't run more than a couple of seconds, and then wouldn't play at all. Not sure which CDI you have, but I traced mine through and found the stator was good but CDI was putting less than 3v down to the coil, if it's any use I can dig the actual figures/sketch I made out? New CDI fitted and fired up fine. 

 

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Do you know anyone with the same bike that you could borrow the cdi from?Would prove it one way or another.Dont know if you've tried disconnecting the kill switch,might have water in it.Seems odd,or very coincidental,that it was fine till you washed it

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I know its not the same application but we blew the CDI on a outboard by giving it a quick start up prior to buying it...got it home and it didn't run... not sure if you started your bike after  washing it but if you did it could well be the CDI...now I always run up so at least the fan comes on and then off before stopping it... 

as mentioned earlier...try borrowing one if you can.

good luck

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No one local to borrow a cdi off sadly but I'm convinced its the cdi. I managed to get an hour earlier and checked the plug to the cdi for the correct pulse from the trigger and the correct voltages from the stator. I will be at it later to check the voltage to the coil with the aid of my special tool (socket adapted to fit into the drill so I can spin the crank) My impression is it's giving a slow pulse to the coil which is less than tick over but that's it! opening the throttle does nothing but foul the plug. I have a second hand cdi arriving Monday or Tuesday so I will report back. The fact it failed literally as I stopped the bike is the weird bit, maybe the act of stopping it with the kill switch was the cause of something in the cdi to short or collapse?  

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 Is the plug wet right away. Sounds to me like the bottom end is flooded. Happens all the time!

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Right folks, it was the cdi. Second hand one fitted and it fired up straight away. I let it warm up and set the idle and mixture screw then put the old cdi back on. Problem was back, ticked over very slow and wouldn't rev fouled the plug and popped back through the exhaust. I found a few wiring diagrams and resistance values online and they all checked out, weirdly the voltage to the coil I had of 3 volts checked out too. The cdi just couldn't supply enough of them to allow the revs to build. Hopefully this may help someone else in the future. 

Thanks for all the help.

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