Learning about two strokes

[WRT]

Cheers Stephen, will be taking my time with it all, thats for sure. Not fussed about adding weight to the flywheel, I've come to love the way that thing makes power!

Sounds like the general consensus is to just get stuck in and replace as many of the bearings and seals as I can spring for. Will do guys, cheers for the tips.

[cheese]

yeah, I just went to get my tyre changed and I had to get a new wheel lock, thingy that goes over the spokes and new bearings and seals.

$200 thank you very much.

[WRT]

What tyre did you go for? I'm going to need a new set sometime soon. Got a lagoona cross thingy on the back, and its pretty damn naff.

[cheese]

I got a a second hand tyre, a M2 or something....

so that $200 wasn't including the tyre!!!!!!!

[WRT]

Ouch . . .

[cheese]

How is the bike looking? what is the damage?

[WRT]

Well, its been a bit of a saga, nothing too major, but will have some pics to show the damage shortly. Doesnt look as bad as I first thought, now that I finally have the engine out (the rear mount runs through the swing arm, and it was stuck in there good . . . finally got it out last night).

Looks like it was the piston skirt (if that is the right name for it) that broke. Only round the back, so that was why the engine was able to keep running despite the noises. Still havent got the crank case in peices yet, hoping to do that tonight. Will post up a more complete story shortly with a pic showing the damage.

[WRT]

Ok, so Wednesday night I get stuck into it again. I start seperating the engine from the frame. All goes well until I get to the mounting point right at the back, where it also seems to be the main pivot for the swingarm. The nut comes off without any trouble, but the bolt wont shift. I'm stood there swearing and cursing and generally beating the crap out of the thing and it just wont budge.

So I called it quits (had to go out for a friends going-away drinks), and just left it there with half a can of CRC sprayed down its throat. Yesterday I caught up with a mechanic mate and got a copper mallet (one of the ones with copper on one end and some other soft matterial at the other) and a punch like metal thing to knock it out. Only had half an hour to spend on it last night, but that was enough. Managed to get the bolt out and remove the engine.

Now that I have the engine out I can see everything a bit clearer, and round the back of the piston, the skirt (I think thats the name for it) has just shattered. I think what happened was some of the bits dropped down and got wedged in around the crank, and thats whats locking it up. When it happened, I was going round a berm, and just as I rolled on the gas this clattering noise started, so I yanked in the clutch, coasted to a halt and hit the kill switch.

When I had done a quick visual on it to make sure nothing was hanging off, I pulled the kickstart out to see if the engine had seized or not. And it seemed to have as it wouldnt budge. But I'm starting to think that it was just that some bits had fallen down and jammed everything up.

I spoke to Botany Honda yesterday, and the piston kit is going to be around $230-250, depending on what type of piston it is (apparently there is an A and a B model). A pair of main bearings is around $50 for the pair, and the seals are around $20 for the pair. Gasket kit around $100, again depending on what ones are needed. If the big end had gone, then apparently its "big biccies". So fingers crossed on that one.

So now the plan is to finish stripping it all down sometime this weekend, and then if its all as simple as its starting to look, then I might get away with just the piston kit and some gaskets. Give it a good clean and off she goes.

But what do you guys reckon, should I replace the main bearings/seals even if they seem ok? Would that be the wise thing to do? And what about the swingarm bearings, should I chuck a new set in there while I'm at it? They appear ok at the moment, but I'm wondering if it would be the logical thing to do while I have everything in peices (especially given the effort required to get the buggers out in the first place). Bearing in mind (ba dum chish!) that I'm not overly flush for cash at the mo, but also that if its going to save me time and money in the long run then I'm prepared to bite the bullet.

And one other thing, in the picture you can see corrosion around the studs, is this normal (for an '01 that gets ridden at Woodhill a fair bit admittedly)?

Cheers guys for all your help and advice.

- Walter

[Motu]

Whoa! Catastrophic piston failure I reckon....wonder what caused that? I've done collapsed pistons just by giving the crankcase a very,very,very good flush out,so long as it hasn't run for too long it won't have damaged the bearings,the alloy piston material is softer than hardend ball bearings.

But,though it's more work and money,personaly I'd strip it and mains and seals all through,and check gearbox brgs.Check your suspn linkage bushes too....never ends eh?

[WRT]

Cheers Motu. Could it be caused by sand getting in when the air filter fell off? I'm starting to have doubts about that now. Or is it more likely to be that the guy before me replaced it with an el-cheapo kit? Or maybe not at all???

I will be pulling it apart to see how things look on the inside. I did think about just flushing it out, but I just wouldnt trust it to get everything out, and plus I'm keen to make sure that there is no other damage in there.

On the flip side, I'm a bit nervous about pulling it all apart, incase the gearbox goes "sproing . . . " and I'm left with a mess I've got no chance of putting back together. While the manual has been brilliant so far, I am just learning all this as I go along . . .

On initial inspection the suspension bushes seemed ok last night, but I was in a hurry and I might just give them a closer inspection to double check. If they are cheap enough (and in stock) then maybe it would pay to do them at the same time.

Still, its all good fun and I am learning heaps about the bike as I go. Next time its due for a piston and rings, its gonna be a walk in the park!

[Ixion]

Gearbox should be straight forward- only thing that typically is a pain is the kickstarter spring. having said that, I don't know your bike. But two strokes are pretty simple. You may have some probs with the big nuts around the clutch area.

Is the broken skirt on the exhaust port side. I saw a piston shatter a bit like that once when the bike pulled a big gobbet of cold water back up through the zorst .

Definately replace the seals, main bearings is a bit more of a judgement call if cash is tight. Depends on how they feel (any clickiness, roughness , junk 'em) and how long they've run. Mains on a two stroke can run very long hours .

[cheese]

yeah next time don't bother taking the top of the cyclinder. You can leave it on and save yourself a head gasket ($20.00).

I'd just grease the rear swingarm to shit. Unless it has some play in it don't replace them. It's EXPENSIVE!! around $200. And you can always do it later. I just had a bearing collapse in my swing arm. Luckily it didn't get completely rooted adn it's still ok.

with the A and B pistons, they are for if your cyclinder is a bit worn (as I was told) the b is slightly larger (as I was told, may be wrong).

If you think that you can get all the bits of piston out with out spliting the case, might be ok, but could be a bit of a risk. I guess you could get a can of degreaser adn blast it in there while holding it upside down, but it's a bit of a risk..... if it was me I'd split it and make sure it was clean as a clean thing on clean day otherwise you may have to push your bike at woodhill again (and that sounds like fun.......)

Have you got a bearing puller? or would you just get the shop to do that bit? make sure you don't drop the crank either!!! a "mate" of mine did that to my old IT175 adn rooted it!! I've got one if you want to borrow it. it's just a $30 super cheap one, but does the trick.

That was odd how your piston shat itself. you are SOOOOO lucky it didn't bugger your liner comletely. Soooooo lucky!!

oh and get a price on a wiseco piston. they are normally a bit cheaper (and stronger!!!)

oh adn while i'm at it. I found that sometimes your engine mounts need to be loosened jut a little bit to help the swingarm bolt come out. Same with putting it back in. Made life a heap easier on my RM.

[WRT]

Thanks Ixion and Cheese, good info in there for a newb such as me (or anyone else that comes along in the future). Ixion - the piston broke on the back, away from the exhaust port. At a guess, if it had broken on the front it probably would have conked out from lack of compression? Dunno . . . but I will do the seals for sure, for $20 its probably a pretty wise thing to do!

Cheese - I dont have a bearing puller, but if they are just $30 from Supercheap then I might shoot down tomorrow and pick one up, handy to have in my arsenal of tools. Cheers heaps for the offer tho. And will make sure I am damned careful with that crank! Interesting about the A and B sizes, hopefully if I just go the same as what is in there then all should be sweet. With the swing arm, I'd removed all the engine mounts except for one a the front, which had the nut off but the bolt left in, just to support it, and still the little bugger wouldnt shift. I gave it a light grease and reinserted it again to let me wheel the bike out of the middle of the garage, and even then it was hard to get back in again. The bearings did look ok, will give a thorough inspection and as you mentioned, just pack it all up with grease. Sounds like it should be ok.

Just a quick question tho (and sorry if I sound like a complete novice with this - but hey, I am!). With the gaskets, if they come off and are intact, do they need to be replaced? The two I have removed so far, have both come out in one peice with very little resistance, like they haven't been cemented in place. So the question is two-fold, can I reuse intact gaskets, and should I be cementing them as I reassemble?

Cheers heaps for your help guys, much appreciated!

[Brian d marge]

Well it wasnt a crank then!!! ,
Starting from the swing arm . Make sure the pivot is ok they can bell out if you use a drift to remove them. Not for no reason people recommend greasing the linkages. ( I have a price list round here for a 2001 I think, I will look up the bits later on )

Cylinder head gaskets, I dont use one . I lapp the head to the barrel anduse a small amount of Loctight 577 master gasket just between the cylinder and the water Jacket.

Sorry I am rushing here as the wife is telling me to get out of bed !!

When splitting the crankcase YOU Need TO USE THE PULLER The cases are very soft and you WILL damage them if you try any other way.

Main bearings will drop out when the assembly is heated properly inthe oven .the will require very liitle help when the case is up to temp.

Pro x do a rod kit which WAS cheap , I dont know about now , BUT as Motu say alluminium is softer than the needle bearings of the crank so you could split the cases , do the mains , and flush the crank ( it hasa wee window inthe rod and you can seethe surface of the needle bearings , check for flaking and excessive wear)

Crank seal are compulsory ,,,

The big nut on the clutch is easier to do with an air gun , but failing that , jam the clutch drum with a rag, use a LARGE socket 1/2 inch drive ...with a Longish handle (put a bit of Strong pipe over handle ) then with a Heavy mallet belt the end of the handle ...Large leverage sudden shock .....that nut can be tight
I awlays do that nut while engine is in frame ,,,but sometimes I foget .....

Anyway glad to see it wasnt terminal !!!!

BTW Cr pistons crack on the thrust face ...due to excessive clearance , and a repeated shock , from where I havent found out yet ,,,,,,I have had 2 pistons with cracks in same place !

Stephen

[cheese]

you can reuse gaskets, but for teh $20 I'd just get new ones. outer cases are ok, but the main one the runs down the middle of the engine and the bottom of the cyclinder isn't worth the hassle of a leak. I reused the one around my kick starter, but then it leaked, was a wanker!! so I used some gasket goo. no leak now!!

oh and I'd just take the split case in to get the main bearings fitted in the shop. save you alot of hassle.

the other day when I pulled my engine out, I got two big bits of polystrene, threw a thowel of the lot and rested the engine on that . makes a nice easy place for it to sit. Oh and even after you have drained the gearbox oil, you still have more oil inside. So be prepared!!! messy messy.

you will have to take the cluch off too and the magneto, so you will definately need a bearing puller. They are a little wanker to get off, you have to hold it still while you undo the nut!!! little fucker!!! and then be careful of the keyway when putting it back on. If you have a manual it will be sweat. oh and take note of where the two lines mark up for the timing. otherwise bike will run like a bag of shite.

oh and another good tip, get a few boxes, adn put all your left hand side bits in one and all the right in another. it make it easier to put back together.

do you feel like you have opened a big old can of worms?