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trialguy

txt 125 E4 stubborn starting

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I'm at ropes end trying to sort out a very fussy 2017 e4 gas gas txt 125, bike only has about 5 rides on it by my 13 y/o daughter and it is safe to say that it is impossible to start for her. To her credit, the count of experienced adults who either can't start it or have extreme difficulty getting it lit, is now 5. For some reason I seem to be able to kick it over briskly enough to get it to fire, but this is not a very workable solution as if she's not with me she's stuck with a dead bike. If I'm with her then riding consists of perpetually needing to park my bike to get her sorted everytime she falls or stalls. A ma:jor pain generally.

So, here's what I know so far:

1) Spark is very weak, unless you spin the motor very quickly (plug out and with hand or foot on kick lever) Anything less than rapid movement gives zero spark.Comparing this with my 280 of same year shows how weak it is, 280 shows a very nice spark with just a modest movement of kick lever with hand.

2) naturally, have replaced plug, platinum tip etc, made sure high tension lead is making good contact etc.  Have swapped cdi *and coil *with the 280 with no difference which led me to the  conclusion that the stator must be bad,  wrong!!  My first rate dealer, Dave of Gas Gas pacific quickly expedited a new hydria stator to me and I thought must  have the problem beat but alas it's essentially the same.** As a side note, coil is the same part number between both bikes, CDI is a different #, obviously different mapping but functioned to give a spark (weak mind you)

3)Of course I've checked the carb, thought of trying a 55 pilot but the bike once running is perfect and besides, I'm already convinced the weak spark is the culprit.

I'm hoping we can get to the bottom of this because it just isn't right and I'm about to pull my already thin hair out!!

Thanks for any knowhow offered,  Cheers

 

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 The Gas Gas pro model has always been hard to start. It takes a technique, you cannot just kick it over and over again. One of the issues, it only has a partial kick start gear shaped in a half moon. In fact my last Gas Gas was bought from a guy that could not start it and he makes his living riding bikes hundreds of miles a week.   

 The 55 pilot is a step in the right direction. Helps to get the piston to top dead center, then a very quick short kick, You also always need to make sure the kick start gears are engaged or the gears will chip.

Edited by lineaway
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I am not familiar with the Hydria system, but if it is functionally the same as the Kokusan, then there would be a ground wire from the HT coil to the chassis, check to see if the connection is a good one. Use an ohm meter for continuity, HT coil ground/earth to the motor, it may be just relying on the coil mounting bracket to the frame. Bye, Peter B.

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Thanks guys, I'll go through the coil grounds (to frame) maybe adding an additional ground wire.  May even try my 280 stator and even the big flywheel, not very likely but has been suggested that the small 125 flywheel might not have strong enough magnetism. Somethings gotta give, never been so frustrated with a bike, especially a new and shiny one!

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check earths. Check the cdi plug in is dry and making good all connections. Get someone who has had a gasser for a while try start it and if theyve got good technique as above it'll point you one way or another. Stators on gas gas arent usually a problem.

Edited by nigel dabster

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 Check all thd pins in the cdi connection. We have seen a few that were out of place, not making a full connection.

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Had a weak/eventually no spark issue on my 18 250. It just decided it wasn’t starting again, then spent ages chasing a spark, checked earth, tang through wiring etc.  Turned out the issue was a faulty CDI unit. 

Apologies for the bad fag packet sketch, and if I’m telling you how to suck eggs, I’m not a fan of anything electrical. If stator/ignition setup is the same as my 18 it may give you some figures from a good stator/wiring to comapare with.

Final confirmation for me I was seeing around 12v up to the cdi when cranking it over, dependant on arm strength, then less than 3v out to the coil. CDI had signs of splitting around the potting so I suspect moisture was the culprit.

 

ED4E3186-485C-4116-87B8-66C6D85A664D.jpeg

Edited by dan929

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Thanks to all the folks who have offered their insight, it's very much appreciated. Still no resolution, I've gone back to the original stator since it proved to make no difference with the new one. I've made sure the coil is perfectly grounded to the frame tabs by filing all the paint off and using conductivity paste. As well, just for certainty, added an extra ground wire from coil to engine. Running an 18 thou plug gap now and have confirmed all pins and connections are good (apparently). No noticeable improvement and spark still appears pretty feeble.  Have the #55 pilot coming in tomorrow which won't help the spark but I pray it helps.  Dealer has ordered a new harness which will be tried next as a long shot.  

still hoping and will update thread at first sign of anything positive.

Thanks again all!

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