Author Topic: what am I doing wrong 74 kx250  (Read 2756 times)

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Offline John Orchard

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Re: what am I doing wrong 74 kx250
« Reply #15 on: May 01, 2018, 07:41:28 PM »
takes a pretty big magnifier to do rotors,usually glass ones  ::), :P


Ha ha oops  ;-)
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Offline Hoony

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Re: what am I doing wrong 74 kx250
« Reply #16 on: May 01, 2018, 07:46:07 PM »
takes a pretty big magnifier to do rotors,usually glass ones  ::), :P


Ha ha oops  ;-)
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Offline bazza

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Re: what am I doing wrong 74 kx250
« Reply #17 on: May 02, 2018, 08:21:05 AM »
Dave put a AJS electrical system on.....lol
Once you go black  you will never go back - allblacks
Maico - B44 -1976 CR250- 66 Mustang YZF450,RM250
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Offline Kane Mcguire

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Re: what am I doing wrong 74 kx250
« Reply #18 on: May 06, 2018, 04:55:44 PM »
Has this problem been solved??

Offline OverTheHill

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Re: what am I doing wrong 74 kx250
« Reply #19 on: May 07, 2018, 11:12:19 AM »
Has this problem been solved??
I see i've my nose in this one back a page so Bump--be nice ta know how it's getting on. Thanks.

Offline 211

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Re: what am I doing wrong 74 kx250
« Reply #20 on: May 08, 2018, 12:01:28 PM »
wife had differing plans for the QLD long weekend so didn't get to it - will do as soon as possible! Imagine the day when I make plans that alter the course of my wife's weekend - that day aint coming any time soon....

one must do as one is told - apparently.....


Offline 211

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Re: what am I doing wrong 74 kx250
« Reply #21 on: June 02, 2018, 04:53:45 PM »
OK
there story is that a new rotor made no difference.
The summary is
carb from my 76 that works fine - same engine it should work fine on the 74
multiple ignition, stator, coil, and now rotor - no difference
port heights look fine, piston around the right way and everything opens and closes like it should
but
it runs like shit - almost nothing blubbering down low, better in the top end but not fantastic. This is the thing that gets me - in all the main seals its the top end that is bad when a seal is gone.
really oily - dripping out so right now Im looking at the right side main seal - thats about where im at short of a crank case gasket leak.......
perhaps the best thing would be shelve the motor and get another and start again!!!!

211

Offline Momus

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Re: what am I doing wrong 74 kx250
« Reply #22 on: June 02, 2018, 05:57:28 PM »
RM370 did the crap running down low when I got it.

New genuine crank seals, checked the mating faces, replaced the center case gasket and the phillips head screws with cap screws to get decent tension- std screws were not tight  (I suspected a possible intermittent 'wet' leak from the gearbox), and it was a lot better. It wasn't until I put a new cylinder and piston on it though that it was 100%.


The original cylinder was ok- ring end gap was well within spec and skirt clearance respectable and so on. Perhaps swap top ends from your 76 to rule that out?

Offline 211

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Re: what am I doing wrong 74 kx250
« Reply #23 on: June 02, 2018, 06:40:54 PM »
Had thought about the piston - its a 40 year old Wiseco and I have never been a fan, it was all I could get. I have another Barrel, have a new sleeve - may be thats the next step after the 76 test??

Offline pokey

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Re: what am I doing wrong 74 kx250
« Reply #24 on: June 03, 2018, 08:24:39 AM »
Rh seal hmmm maybe.. maybe nor. Would have noticed the hot car smell from different oil . Gearbox oil also goes milky.

Leakdown test would verify bottom end.

Have we burnt the pipe out lately? A carboned pipe wont make it run fabulous and with all that unburnt oil im guessing the pipe isnt doing its job.

Offline evo550

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Re: what am I doing wrong 74 kx250
« Reply #25 on: June 03, 2018, 09:20:34 AM »
When you did the carb swap from the 76, Did you bring across the slide/needle as well or just the carb body and used the 74 slide/needle?

Offline bigk

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Re: what am I doing wrong 74 kx250
« Reply #26 on: June 03, 2018, 09:37:15 AM »
If you don't like Wiseco, use an Elsinore 250 piston (used them in '74 KX a few times), of which there are other brand options.
K

Offline OverTheHill

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Re: what am I doing wrong 74 kx250
« Reply #27 on: June 03, 2018, 11:01:01 AM »
Was just going to get my teeth into this [most teeth mithing] but see i've rambled on back a page so i'll just re-run it as pretty much covers my thoughts. loved the one i rode when new or almost new--must have a pic somewhere, front wheel in the air passing my boss on his yz360b mono up a track. Hope ya get it sorted. Not reed valve so can't have piston back to front--well can but not the problem. Someone [apprentice] not made a base gasket for you & omitted to cut out for the transfers?, don't laugh i've seen it happen, ran but only just. Ok, wifey's home--yes dear i've been busy!!--panic. Just reinforce cleaning the exhaust & if in doubt then cut it open or at least slide a garden hose or something down the tail pipe to be sure she aint restricted at the weld where tail pipe joins. Plus be sure of muffler internals. Got caught out once on a GoKart which went like hell i thought but not compared to another identical Racket motor or something with a vacuum power valve & muffler was collapsing inside & partialy blocking the pipe.

If it starts & runs [i think] the problem lies elsewhere. CDI spark never looks 'that healthy' but would make ya hair stand on end--or fall out. No chance of something 'accidentally' left under the seat restricting air cleaner air flow. Sounds like restricted exhaust as another option, or main jet fell out or slide needle still sitting on the bench. Sorry if that sounds a bit off but more or less just letting the cat out of the bag to all the cock ups i've made over the years lol. & just when i think i've covered the field of cock ups i go & 'discover' a new one. If it's definitely electrically missing its bum off then ok--i give in & ignore all my rambling. Just tend to think if it starts--it's ok--unless they have a high speed winding separate from the initial source coil but think you said swapped stators so that ideas out the window. Cheers [or tears]. ps, i road one of those for a few meets back when new & was a very enjoyable time too--well till a rear brake shoe spring broke & locked the wheel miles from the finish of a long distance race. Very willing motor.
« Last Edit: June 03, 2018, 11:09:51 AM by OverTheHill »

Offline Slakewell

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Re: what am I doing wrong 74 kx250
« Reply #28 on: June 03, 2018, 05:23:38 PM »
Maybe the crank shaft is bent? Letting air in? I hope to see you at CD Dave for a beer or two. Come over and take the A4 for a few laps.
« Last Edit: June 03, 2018, 05:37:10 PM by Slakewell »
Current bikes. KTM MC 250 77 Husky CR 360 77, Husky 82 420 Auto Bitsa XR 200 project.
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Offline 211

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Re: what am I doing wrong 74 kx250
« Reply #29 on: June 04, 2018, 08:35:55 AM »
thanks all
going to burn out the pipe and see whats going on - full report soon
appreciate all the help!!
Mick - going to CD on Sunday for a look - possibly riding the H2 but not riding at CD, see u there.