Learning about two strokes

[WRT]

I've learnt a lot about two strokes since getting the CR. I've learnt they are noisey, smokey, and shake like a crack whore with the DT's. I've learnt that they are a lot of fun to ride hard, and with a powerband comes on like a lovetap from a sledgehammer coupled with a throttle like a light switch, that they demand respect from the rider.

Last Saturday I learnt a few more things about them. I learnt that if they start sounding like an Italian tank running sans oil, then best hope your not too far from home. And that you cant believe the advertising propaganda - if you want to know how much your bike really weighs, try pushing it over a sand dune.

Also worthy of mention is that after pushing said bike over said sand dune, dont go playing paintball. You will be too tired to make rational decisions as to what constitutes a safe barrier to hide behind and will wind up copping some bruises as a result. See evidence attached.

So last night I thought I would learn some more. I had my first attempt at stripping down an engine in quite some time - my last effort was a rebuild of Morrie Minor thou engine, about a dozen years ago or more, and I gotta tell ya - this is a whole other kettle of fish. First impressions were good, two strokes are simple engines and very easy to disassemble. To the stage in the photos took an hour, and that included me finding my way, and cleaning all the bits that normally get missed while the bike is in one peice.

Looking a bit closer at the damage to the internals, my original hope that I might be able to get away with stripping the engine down in place proved somewhat diminished. Little chunks of metal are spread throughout the engine, through the chamber and into the exhaust. The piston is well shot, but thats not too upsetting, it was getting time for a rebuild anyways. However, the piston wasnt stuck to the bore (which, surprisingly enough, looks completely unscored), instead something down within the crank case seems to have been the bit that let go.

So possibly looking at a big end or something like that. I called it quits at the stage you can see in the photos, and it will be Wednesday night before I will have chance to do any more work on it. At that point I am going to pull the rest of the engine out of the frame, and strip it down good and proper. Meanwhile, I am going to head out to grab some lube for when the bill comes in for the parts.

Still, at least I'm learning something from it all I guess.

[k14]

Piston doesnt look too bad. As long as the barrel is alright you should be able to get away with a new piston and rod kit. I assume you can get a new rod and big end put onto the crank etc. If you can I think it should be less than $500 to get it up and going again.

What is this "sans" oil you are talking about? I'd recommend shell advance racing, never had any problems in my rs and the engines aren't too dissimilar.

[WRT]

The barrel seems to be ok, was pretty nervous about it after reading in the manual about how the coating on it means its a throw away job if you get it scratched. But it seems mint.

Still got to get into the bottom of the engine to check the big end and crank etc, but there were some fairly chunky bits in amoungst the detritus scattered around the engine (see the cup in the middle of the parts, those were just some of the bits I pulled out). Dreading to think what the damage might be down there, but I'm keeping my fingers crossed.

And by "sans", I was meaning without. She was making some almighty rattling noises. As soon as I heard them I pulled the clutch in and hit the kill switch. After that she was a no-go, first thing I checked was if she would turn over, but she was seized up tight as a drum.

[sAsLEX]

What is this "sans" oil you are talking about?

You never did pay attention in Latin did you, Mrs Atkinson would be most dissapointed


sans Pronunciation (snz, sä)
prep.
Without.
[Middle English, from Old French, blend of Latin sine, without and absenti, in the absence of, ablative of absentia, absence, from absns, absent-, present participle of abesse, to be away; see absent.]

[WRT]

Hard to make out from this, but the barrel is nice and shiney, and seems to be scratch free. The surface is smooth as. Is there anything I need to do to it to check it other than just running my finger over it?

[Ixion]

Nope, if it's a coated bore and no visible damage it's almost certainly good to go.

Piston's obviously a goner. You may or may not need to replace the big end, might just be bits of ally got into it and jamming.

Replace the crank seals as a matter of course, and the little end if it has a roller gudgeon. And make sure that you get ALL the little bits out of the bottom end AND the zorst, cos they can come back upstream and bite y'.

I've learnt they are noisey, smokey, and shake like a crack whore with the DT's. I've learnt that they are a lot of fun to ride hard,

Yep, that's two smokers !

and with a powerband comes on like a lovetap from a sledgehammer coupled with a throttle like a light switch,

Not all two strokes. Petal pulls like a train from 1500 rpm (about 55kph in top) , and the power is progressive all the way to peak - no discernable power band (that's the CV carbs, the earlier ones had more of a power band effect, still nothing to speak of)

[cheese]

ah if it's got mo major scores you'll be fine.

have fun splitting teh crank!!

guess you don't want to come out to woodhill this weekend then....... unless you manage to get it all doen really quickly......

BTW, your engine is so similar looking to my RM's it's not funny.

[WRT]

Thanks for that Ixion, funnily enough I'm actually looking forward to Wednesday night when I pull it all apart, just for the learning curve and also to see exactly what has gone wrong. Will definately check out all parts while I have it stripped down that far, may take me a little while to put it all back together because I am just working it all out as I go along.

Thing is (and this is a little too coincidental for my liking), the last ride I went out on the airfilter fell off somewhere along the way. Naturally, I only realised this when I get home and pull it apart to clean the sand and crap out of it. I suspect that the sand has gotten in there and really messed something up. Lesson learnt from that too - always make sure your filter is done up tight.

And the CR has only a tiny amount of power down low, but when that powerband comes on, make sure you got a good grip on the 'bars . . . the combo of 60 odd hp and around 90kg makes for a wild ride over rough terrain. God I love it . . .

[k14]

Hard to make out from this, but the barrel is nice and shiney, and seems to be scratch free. The surface is smooth as. Is there anything I need to do to it to check it other than just running my finger over it?

Yeah looks pretty sweet. The plating on them is nikasil, you can get them replated but you have to send it over to the UK somewere and the process isn't bulletproof, alot of the 125 guys just buy a new barrel when it wears out.

You should get a new little end etc with the piston kit. Do you know how long it has done on that piston and crank?

[WRT]

guess you don't want to come out to woodhill this weekend then....... unless you manage to get it all doen really quickly......

Yeah, I wouldnt hold my breath if I was you! I'm going to do my best, but havent even got to the "ordering parts" bit yet, so will have to see how things go. Plus have two weddings to go to this weekend, but if the bike was running rest assured I would be trying to slot a ride in there somewhere.

Be real keen to meet you up there for a blast one weekend tho. Been on a few road rides with KBer's before, but no off road ones yet.

[WRT]

Bang on there, K14. The barrel is coated with Nikasil, and the manual reckons its a throwaway if you scratch it, so I breathed a sigh of relief when I saw it looked pretty intact. Supposedly (if I can believe the previous owner) it should be sitting on around 50hrs on the piston now, but no idea about anything else in there. I'm thinking I might do a few bits on it while I am at it, like the reeds etc. Like I said, its all a learning curve for me, but still, good fun and I'm really getting to know the bike now!

Plus its a great time to clean all those hard to get to places!

[k14]

You never did pay attention in Latin did you, Mrs Atkinson would be most dissapointed


sans Pronunciation (snz, sä)
prep.
Without.
[Middle English, from Old French, blend of Latin sine, without and absenti, in the absence of, ablative of absentia, absence, from absns, absent-, present participle of abesse, to be away; see absent.]

Shut up, didn't learn anything in that stupid class anyway

[Motu]

Sounds like a bearing has gone somewhere....little end,big end or mains,I'd say big end at a guess.Do them all anyway,they are fairly cheap,although there are gearbox bearings to factor into it when you strip it completely.I hope you can buy a big end - Honda has a habit of supplying ''crankshaft assemblies'',but being a supposedly race bike big end seperatly should be available.Good luck with the rebuild - and keep it clean please.

[WRT]

Cheers Motu, will be doing my best to keep it clean, and keep the sand on the outside from here on in.

At least once this is all done, I will know everything is right on the bike. And that if anything does go wrong that I can fix it myself.

[Brian d marge]

Hi there
Well I am on my 5th big end right now , Excuses ranging from crap oil to heavy right hand.
Hondas crank ...hmmmmm Hate them , they CAN be rebuilt , BUT you need a jig to assemble them as they have a tinny plate to take up the volume which is easy to destroy ,
Over here they just replace the crank assembly , Pro X do a reasonable Rod bearing assembly, If you can find a place that will rebuild a Honda crank,
( Me I am either going to ship the cranks to a place that will rebuild them Or make a jig myself and rebuild them Myself, - most likely this is the way I will go as I want to be self supporting by next year -

The power delivery can be made smoother by the use of a flywheel wieght. I made my own as the american one were expensive, I made my own for about 150 NZ, It really helps the power delivery in the tight stuff.

When rebuilding . BE CAREFUL with the power valves they are a PAIN to time ....The engine will run but it will make NO power , I have the earlier engine ( sticking with that cos its and sleeve not plated , and my are the slide type power valves , and they will open and close with gas pressure , making you think its timed correctly when it isnt !!!

When refitting the barrel DONT FORCE it , its real easy to bend things

If it is the crank let me know how you get on .

Ixons post is spot on , replace those crank seals as a matter of course , they are asy and cheap to do , Oh and the main bearings if you budget can stretch , the CR ones arent much cop.

Me ...I would like to put my 91 engine into the newer 2005 chassis ....anyone have a 2005 chassithey want to sell????

Stephen