Bought a dud cr 250!

[crfudge]

Hello just joined, my names grant and hi to all!! I Bought a 1990 cr 250 yesterday, guy lived in a town so couldent test it out, just drove it up a road when it was cold that was that. it took a few kicks to start. Anyway went to go out on it today and kicked it and kicked and kicked!!! put a new plug in kicked and kicked u get the picture! Heated the plug kicked about another twenty times and it fired! Yipee let it warm up for 5 mins, took it out in the fields still felt cold, drove it about and opened it up just kept running like it was cold!! Just seems dead on power, then it got worse, got it close to home started being real bad pulled back the throtle hardly any power, then it was like it had a rev limiter puut puut puut on it! Switched it off tried to kick it to see if it would start when hot guess what nope! Please help me!!

[mr.tattoo]

sounds like a top end rebuild dude, or rings at the least, no biggy, quite cheap and easy to sort yourself though

[crfudge]

When u say top end rebuild, do you just mean striping and cleaning or replacing the piston, when u said rings could be the worst case? Before i rode it i did a bit of maintnice to it, one of which was putting on new exhaust springs. The bike shop didnt have any exhaust o-rings so i tried to make to with a sealant, it was blowing a bit at the manifold but this would'ent cause such big running issues would it? When i was tring to get it to start inspected the plug for a spark and noticed it was non-exsitant till i gave it a hard kick??? It was a new plug too.

[T1z3R]

blowing at the exhaust port can cause major issues since your bikes a 2T. get that sorted out first.
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duck my sick!

[mr.tattoo]

most older two strokes leak slightly from the front pipe mate, the symptoms sound like piston and rings jobbie but check the coil, new plug ect first to find out if its sparking ok, if yeah then id personally just slip the top end off and have a look, it could be a load of things, powervalve sticking ect... good luck

[crfudge]

Hey thanks for your replys!! i took the carb off and cleaned that, and took the magneto off the four contact points are just metal i'm not sure if they should be covered in a brown coating??
i've managed to get a knack to starting it a bit better but i'm giving it a really hard few kicks, throttle wide open and the choke on. When it does run its just so dead on power! i've put a new plug in and its sparking but only if you give it a decent kick.
On the piston side of things i can turn the magneto wheel thing, by hand with the spark plug in should it have more compression than this? I presume its the piston too, just want to make sure its defenitly this before i then have to buy new gaskets etc for nothing. When i take it apart how do i know if it or the rings are past it?? Thank you!

[T1z3R]

although mr. tattoo probably (read = definitley) knows more about bikes than me id be checking the exhaust first as its the easiest thing without having to buy parts...just make sure its tightly done up and that theres a good seal.

then again if it has a good seal and is only blowing slightly then its probably got nothing to do with that but its just a suggestion.
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duck my sick!

[mr.tattoo]

mate check anything that looks suspect, the exhaust could be a posibility but without the bike in front of me is quite hard,, if you take the barrel off look for worn sides on the piston and ring/s and check the barel for score marks or worse check all the easy and cheap bits first before you remove anything out of your capability..... if you get stuck or sumink feel free to email me pics ect if your unsure if parts are broken and things good luck and remember 2 bangers are the best!!!!!

[crfudge]

Hey thanks very much, i sealed up the exhaust no difference just dead on power!! Pull back throttle right back and just feels like it reaches half revs then a limiter comes in puut putt putt! I'll strip it down tommorw and inspect the piston. Thank you for that kind offer and your help!!

[lee125]

hi if you want to do a quick check at the piston just take the exhaust off and look into the barrel were the exhaust joins to see the piston for scores e.t.c as above
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cbt passed 01/07/2006 bike:92 dt 125 and 96 honda cr 250
theory:PASSED! A2 test:PASSED 08/11/2006 restricted to 33bhp for 2 years

[crfudge]

Just taken the cylinder off, theres marked but no scores, its been resleved, it looks a bit messy round the ports. Bad bit is the piston has been hitting off the crank!! Whats going on here? bottom of the piston's dented.

[crfudge]

Took it to the bike shop, guy said the piston is slack which it is and thats why its hitting the crank. I wanted to get away with just honing it and an oversize piston but he says rebore it? Do u think i should bother? I probably will though! Wheres the best place to buy a cheapish oversize piston, dont want to spend much on this bike as its old and just a toy, not a racer. Thanks

[T1z3R]

try www.trmracing.co.uk for parts.
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duck my sick!

[crfudge]

Thank you!!

[crfudge]

just been to the bike shop, my barrel is nicosil plated which means that when i have it bored i need a different type of piston, They were pretty unhelpful, what sort of piston would i need? I also found out the engine is an 87!

[T1z3R]

phone TRM and give them your engine and chassis numbers and they'll tell you what parts you need.
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duck my sick!

[crfudge]

hey yeah i phoned them before i went to the bike shop, there really helpful, thanks for recomending them. Went to the shop to get my barrel measured ending up going to agra engineers and done. Going to get a 1.5mm oversize. Next one now is the bottom end seems to have play. not sure how much movement there should be but there is!

[mr.tattoo]

if its re-nickle sealed you shouldnt need to go oversized mate as its not like a rebore its a resleave type jobbie??? and there is normaly slight sidewards play in the big end bearing but should be no up or down though!!

[crfudge]

They said they would bore threw the nicsle till its normal metal then i can just put an oversize piston in suited to cast iron? So do i need to be getting it plated, is that not expensive, do u think i need it just for a field bike? With the bottom end there seems to be the slightest slightest up and down, but a bit of sideways maybe 2-3mmis this okay? Thank you so much for your help i really do appreciate it all!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

[crfudge]

Just been reading that i need to modify the powervalve with getting it bored? I didnt mark a postion where the valve came off the bike as it has a spindle with teeth, do i need to "time" The valve to the bike when i put it back in?

[mr.tattoo]

ive heard of people boring past the nickle seal and just oversizing but personally ive not done this before , ive just got the barrel re-plated in the past which is around 60/80 quids you normally get sideways play but you shouldnt really have any up and down, id replace the bigends dude if theres play or it could go horibly wrong

[crfudge]

I really appreciate you helping me! The internet may be getting cut off for a bit so if i disaper its not like i've just come and got info then just left the site and not returned anything, just incase thot i'd say! How the hell do u get the big end bearings done, take it the engine getts split in two but how does the crank split?

[crfudge]

This gets worse! Been phoning about for a piston and just been told that i cant over bore. Behind the nicosil its aluminum not cast iron so i cant bore it and have a oversize put in. ARGGGGGG i just want to fix this and sell it but even thats going to cost me!! Anybody know what i can do to make it run without plating? the bore is slack!

[T1z3R]

how much for a new barrel and piston kit then?
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duck my sick!

[crfudge]

havent even looked at a new barrel , i've found a place that will replate mine and match a pston to it for £170 But thats with out repairs if needed and then gaskets on top of that. Its just not worth it for such an old bike! want to get it measured again and just try and get a slight oversize piston, that wil be £60-£70.