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Discussion Starter · #1 ·
Any clues amigos?

Was running fine til a few weeks ago. Now revs fine up to around 9-9.5K then acts like the ignition is cutting. Will eventually struggle thru to around 10.5 K but a long and not very pleasent sounding/feeling experience.

Got an inkling it may be a dodgy electrical connection - coil/cdi/HT lead etc. or earth tag maybe. Whipped the carb out stripped and cleaned - still the same, plug colour not giving much of a clue as rough running is akin to doing multiple plug chops! Its a new plug by the way.

Think I've done all the obvious things and its prob just a poor connection somewhere (been wiggling wires left right and centre on the off chance I find it), but if there is anyone out there who's had something similar please point me in the right direction.

Gutted that just as the engine starts to make decent power it runs rough!


Ride safe my little ones!
 

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Does not know Everything !
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Rings okay, compression test ?
 

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Sargent Sarcastic
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Rings okay, compression test ?
Aye, mine started with that carry on. Got worse, would not rev past 7k then was doing about 10mpg and would not go past 65-70mph no matter what. Did a strip down and was about 1mm between the ring and the barrel, was no compression me thinks
Bottom end survived though so not all bad.
 

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Yup, performance will start to drop off gradually and will get worse faster and faster until you struggle to maintain 3'ooo rpm.

If he just had it rebuild however, should be easy enough to check.
 

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ruffidge bana'

i hope for your sake its not low compression. i cant imagine its your pv as your getting past the key 6.5-7.5 pv actuation point - whats the performance like through that rev range??

besides that, as has been said, change plug, check gap, check coil lead.

What kind of temp are you achieving before trying to rev out??? - tis cold in these here hills lol

T
 

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Discussion Starter · #10 ·
Firstly - thanks for all the input - ideas greatfully recieved!

Sadly, none of these ideas seem to be the problem.


Was doing it on old plug - brand new Iridium one did exactly the same - gap is correct.

No Compression prob - checked it only about a month ago and (from memory here) was somewhere around 120 - which suprised me cost the previous owner did little/no maintenance and I was expecting to discover it was due a barrel change!

Removed the whole PV assembly about 3 weeks ago, replaced blade and cleaned everything to a sparkle. Still the same problem!

Unlikely it's coked up (did the pipe a couple of months ago and that wasn't too bad). This fault has just come out of no where - there's been no slowl drop off in performance which would point to it.

Don't think its jetting - its not at exactly the same revs in each gear - prob around 8.75K in first then sorta rises with the gears to 9.75kish in 4th/5th etc. The missfire comes in very abruptly as well, in that it doesn't start missing a little, and gets worse with revs, its literally like a rev limiter coming in and killing every other spark.

As for power through the band - seems ok. Obviously pulling away low revs its sluggish, but is fine pulling from around 4k when poodling around in traffic, and over 5.5K it revs up clean and srtong as ever.

Oh, and just as it was asked, I don't start giving it some til its properly warmed up. Live in town, so not very often I can pull out of the driveway and give it some right hand straight away!


Its a bit of a head scratcher this one. 2/1 its a dodgy electrical connection somewhere, maybe a duff HT lead or CDI. Don't want to spunk ?25 or so on a second hand CDI only to find its a duff earth connection ot loose wire on the crank position senser.
Think its bound to be something stupid. Anybody got an idea of the engine timing across the rev range. Just wondering where in the range it starts to retard the ignition as it may be a clue!

Thanks for your time chaps - ride safe and mind that ice!
 

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"No Compression prob - checked it only about a month ago and (from memory here) was somewhere around 120"

120 psi is low. You want about 150/160 psi.
 

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Actually... my bike used to do that, it started off doing it only at high revs 9k+ then it got worse and started doing it at the lower revs.. and finally it just wasn?t drivable at all! According to my dealer - it was the wires connecting to the CDI unit, they needed re-seated.

That may not be the case for you but worth taking a look.
 

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Hi !

have you cleaned and maybe up-graded the little wire that goes to sparg Coil ?
(im talking about the Coil that has a sparg plug at the end..and has also a little wire attached into it. The little wire is Black-White color if i remeber correctly..If this little mentioned wire hasnt got a good connection, it will cut the ignition now and then...

I have also once seen a semi broken CDi-unit that had semi broken coppercore in it. All the wire's looked perfectly ok. from outside but the copper inside in them was semi broken.

bye !
markus
 

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Discussion Starter · #15 ·
Thanks for those 3 post fellas, I think you could be in the right neighbourhood there. Will have a proper goosie at the cdi/coil wiring.
 

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BANANAS!!! Mine was/is (not ridden in a couple of weeks) exactly the same thing. I had mine re-built and stage 2 tuned by Stan Stephens, was running ok when running it in then the day came to give it a bit of wellie. Went a treat, powervalve the works! Next time I went to give it a thrash I got your problem and as you described it got worse and worse. I changed the spak plug for a new one and all was good in the powerband neighbourhood!! Then just recently it's started doing the same thing again. Sooooooo, this does not really answer your question but it could be it's eating plugs for whatever reason or where I removed old plug I upset wiring and it worked find and after a while wiring has buggered up again. When I get chance I'll do some trial and error on moving wiring and new plugs! But until then.... keep us posted!
 

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Discussion Starter · #17 ·
Will do.

Can't be doing much to it at the mo as I can't risk it not running - car's MOT has run out and not had the time to sort it yet
so having no transport would be a disaster.

Maybe the weekend will afford me some tinkering time.....
 

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Discussion Starter · #18 ·
Just to let you know (if you care that is), problem is solved!

Got a replacement Coil c/w HT Lead and new plug cap (ta to MME), whacked them in, trimmed and fitted new crimps on the various wires associated and lo and behold - running sweet as a nut again.

YAY!!!!


Thanks to everyone who posted possible solutions.
 

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120 psi is low. You want about 150/160 psi.
LoL! 120 is NOT low. Anything below 100 and yeah new rings. 120 is fine.

160 LoL - What you running - race fuel?
 

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120 is low enough to make me wanna rebuild it personally. a healthy engine should be putting out a 150-160 as old painless said. you dont need race fuel untill your a fair bit over 160psi.
 
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