Big problem this time - bike sounds like a sewing machine and no power

**Mole_C** · 23rd October 2006, 22:43

Nice work, maybe i shld try take mine apart sometime

Na, ill probably break it all :P

With the idle thing you don't have a little knob to turn the idle level up and down do you? Mines on right hand side near where you put the oil in. It could be as simple as turning that up a click

**xwhatsit** · 23rd October 2006, 22:48

Yeah I've tried a variety of adjustments to the idle level since I've had it (first of all because I'd never used a manual gearbox before and kept stalling it when I went to take off ^_^). But no... I can get it to reliably idle at 2500+, or 3000+ to be safe, but anythign less than that, it will stall within 30 seconds. I'm not sure if it's missing or anything. Suspect it probably has to do with the sparkplug once again, it's not sparking well enough so it misses, and when it misses at low rpm multiple times it doesn't have enough momentum to keep going. Will worry about that later, once I fit the new head (if I can find one!), and set up the carb properly.

**Posh Tourer :P** · 24th October 2006, 02:32

with a weak spark, it is quite likely it won`t idle.... I would check the coil (the HT lead comes from it) and see if it is damaged at all. Also see if you can get another one to try in its place. Check the HT lead for physical damage too. You might just take the HT lead off the coil and make sure there is plenty of copper showing on the contact area. Also try checking the battery and replacing that. If you have a multimeter, check the voltage output. That shouldnt have an effect, but it might if it is really bad. Points can also cause problems. Under the right hand side engine cover (IIRC).. These are cheap to replace and wear out commonly. Check that they are clean and making contact face to face fully and that they arent offset.

That should keep you going for a while. If it isnt one of those problems I'm a bit stumped.... Does it foul plugs more when you ride with the headlight on??

P.S. I've sent an email, I'll let you know...

**xwhatsit** · 24th October 2006, 10:59

With a fresh plug I get a nice big blue spark when I kick over the bike with the plug out; with a plug I've ridden more than 100kms on there is non-existent/very weak spark.

I'm not too worried about this bit yet. The cylinder head crack is right next to the spark plug socket so maybe something is going on there.

Cheers for the email, Mr Tourer! I've just got replies from two of the wreckers I contacted earlier and they have nowt.

**lb99** · 24th October 2006, 18:40

Did you buy it?
I had a CB250RS about 15 years ago, cracked head and all.
use the rev counter drive out of the Cb250 in the XL Head, Im pretty sure the valve timing is just line the crank up to TDC, put the cam in LOBES DOWN and put the chain on the sprocket so that the marks line up with the head, then slip the sprocket on to the cam, and do all the bolts up, dont use the rocer cover studs to compress the valve springs or you will strip some threads(trust me, I know

)also make sure the oil feed to the head is unblocked . I cant remember if the XL had a different cam profile, but the XR did Im sure it was wilder, the XL,XR,and CB all have the same bore, but have different compression ratios, and gear ratios too.
My CB went fine with an XL250s bore, piston, head and cam, they are pretty simple and rugged motors, I used to seize mine quite regularly, always just waited until it cooled down and it always fired up easy as, as you can guess, I had a top end rebuild down to a fine art.

**xwhatsit** · 24th October 2006, 22:03

@lb99:

Great story, man! From your avatar it looks like you have the same taste in bikes I do ^_^. Yeah I used the same basic technique to put the engine back together (knowingly with the cracked head; I've done about 50-60kms at least after putting it back together, it doesn't seem to be getting worse thank god). I used a spanner to hold down the valves (god that spring is stiff) and borrowed somebody to take the little collets (sp?) out.

I didn't know the XR250 had the same/similar motor as well? Hmm. Yeah I noticed the XL250S on Honda's Japanese website is rated at 20PS, while the CB250RS is rated at 26PS or thereabouts. I don't need to replace the cam yet but I'll keep that information in mind. I did hear that later CB250RS models had more power -- 33PS -- could this be due to cam profile? Might be interesting to investigate that.

Hahaha why do you think you seized it regularly? I hope I don't end up doing that

. Will have to keep an eye on the oil changes.

No I didn't end up buying the XL250S (if that's what you meant). I was counting on ~$200, but it ended up selling for ~$400. I've just been quoted $175 from Econohonda (yay! Somebody has one!) but won't purchase it yet until I hear from some other people. $175 is a fair bit of money from a student hahah so I want to make sure I can't get it for cheaper first.

Motu earlier mentioned that I may have bent a valve too. It looked fine to me when I pulled it out but then again I don't know much about mechanical things yet. How is an easy way to tell? Is it something I can see with the naked eye, or will even a minute bend in it cause problems? At least valves look significantly easier to obtain than heads.

Thanks, everybody.

**gijoe1313** · 24th October 2006, 22:15

Yowsa! Sounds like you are getting down and dirty with the innards of your ride! On ya! Nuffink like doing the business for yourself and kudos to those who know what they are doing and giving ya some hard won advice!

Hope you spend some time riding it! The only thing better than being a Tree-shade mechanic is getting out in the sun and riding

Keep up the good work and Make Peaceful Running of Soundful Motor So All Your Ride Will Belong To Us!

**xwhatsit** · 24th October 2006, 22:28

For Great Justice, Launch All Camshafts!

**T.W.R** · 24th October 2006, 22:45

sounds as if you inherited that problem from the previous owner and it's lunched itself on you

commendable effort getting it running again, wouldn't use the bike though until it's fixed.

safe enough to trackdown a replacement head from any of the XL/XR 250s (XL250S through to XR250RB)from 78-83ish most of the variations were with cam profiles in the head itself, other changes came from carb size differences, & lighter cranks in post 80 models etc.
The 84 XL/XR RFVC heads were notorious for cracking, not the earlier ones.
you don't have points either, it's all controlled by a ATU rotor & CDI

**lb99** · 25th October 2006, 12:33

I seized mine coz I brought it (at 17) sight unseen, of my girlfriends brothers mate, and never even thought to check the oil, and rode it home over Kilmog Hill just out of Dunedin, I was flat out going down this long straight downhill when I noticed it was loosing power, next thing......lockup at 140+, sure enough, no oil

, on that bike I learned a lot of things, the top engine mounts kept brakeing because the frame was sooo bent that if you drove though a puddle you would leve two wheeltracks behind, no problem, get engineer to make engine mounts out of 4mm plate, then go back to engineer to get him to helicoil all of the rocker cover studs that stripped when the motor kept trying to tear its self loose from the frame, tried this several times before I gave up and put up with the motor moving about a bit on its mounts.

I learnt that you cannot do without a gudgeon clip, it only takes 30 km on the highway to make a nasty score on the cylinder bore( enter another bore and piston), I learnt heaps of things on that bike, eventually the big end went and I sold it to some schoolboy who was keen as, and brought an NSR250

**xwhatsit** · 4th November 2006, 22:08

Bah well I think I've killed it this time. Well, not killed it. But injured it rather badly at least.

Recently it had been getting louder and louder, so I looked where the exhaust attaches to the head and noticed that the big plate of metal holding the exhaust to the cylinder head on the right exhaust was hanging off at the bottom. Upon closer examination I saw that the bolt had actually come right out of the head -- kind of worrying seeing as the bolt is supposed to stay in the cylinder head and you wind a nut onto it to hold the exhaust in. Pulling it out I noticed a whole lot of metal shavings inbetween the threads on the bolt, so it has been stripped, maybe a helicoil put in (I don't know what it looks like, I'm only guessing). So I wound it back in as good as I could with some pliers, bolted it all back together, started it up, and although it's still not 100% sealed (if I put my hand in front of the head I can feel air flow pulsing in time with the engine firing), it's a hell of a lot quieter.

Anyway, coming home across Mangere Bridge about 20 minutes ago, passing some cars, revving it out to 6000-6500rpm to pass some cars. Felt good, really powerful, awesome, and a lot quieter of course haha. Turning off onto my onramp, there's a long straight bit before the lights and I just let go of the throttle and let the thing engine brake in 5th gear from 6000rpm to 3000rpm before shifting down. Somewhere at about 4500-5000rpm the thing started making this godawful clatter that sounds quite familiar. However, I'm not 100% sure but it doesn't seem quite as bad as before, and power loss seems a lot less. I wondered if the exhaust had come out again but a quick visual scan seems to say nothing there, and it doesn't have the loud Harley/tractor type pot-pot-pot noise it did when the exhaust was semi-open before, just a horrible clatter like when the valve got fscked before.

So yeah... I knew it would happen eventually (you can't ride on a cracked cylinder head for ever lol), but I was hoping I would make it until after exams. Pain in the arse. I'm impressed it held up that long though lol... I think I've become a life-long Honda fan (yeah I know they're not the most manly bikes, but I think it's pretty cool that I can abuse it like that (lb99 seems to know how to do it too hahah) and it took maybe 800kms before it died).

Good thing I love riding it so much, or I might not be so forgiving of the old gal...

**lb99** · 4th November 2006, 22:45

get yourself another cylinder head, an XL250 one will do, but it will probably be silver, if its chucking valve seats away then its definatly rooted, the crack in my head was between the plug and a valve and just made it a bit smoky, oh, and do the exhaust studs up before you do up the rear exhaust mount, then you dont have to use them to bend the pipe, abuse away, the top end is a piece of piss, but the bottom end is as tricky as fuck (balancers and chains and stuff

)

**xwhatsit** · 5th November 2006, 01:21

Yeah the crack I've got is there too, between the plug and a valve. Do they do this as a matter of course? Is it a XL/XR/CB250RS `thing'? Bloody bloody bloody...

Yeah I've been trying to find a head anyway, I can get one from Econohonda but that's $200 which isn't easy when you're a student. There's another man who may be able to help me for (hopefully) less dollars but I will have to wait a while before he will have time to have a look.

**lb99** · 5th November 2006, 07:55

but its the same head, so its probably common, I know a Honda nutter down here who might have one, whats the cam like? are the bearings still ok?

**xwhatsit** · 5th November 2006, 11:09

No cam bearings

... the thing just runs directly on the head. Even somebody like me who doesn't know much about engines was surprised to see that... the Haynes manual says some people do/did conversions to roller bearings. But no, there are no bearings for the camshaft, if that's what you mean. The top end looks in pretty good shape... possibly there's a bent valve (or two now, if it's the other exhaust valve this time), but I certainly couldn't notice it when I pulled to pieces.