KTM 380 - rebuild req'd? Help a 2T n00b.

[2TInstitute]

The only thing you should drive up to Aurum to do is to turn the power off on that blokes plating shop. Have only heard of 1 cylinder he's managed to get the plating to stick to. You can if you want but be warned you WILL be sending it to another plating company.

I should be able to fix it you can either send it down or send it to Millenium, but sorry I don't really reveal my 'trade secrets' on the internet. You only have to pay the postage

[mugget]

PM sent.

If you reckon you can fix that plating area well enough so I can install a new piston and have it last 50+ hours I'd be pretty stoked with that!

[Jeram]

Im back from OS so let me know if you still need any more 380 info

[mugget]

Ok, getting back onto this now, trying to get everything organised for one final parts order. Just wondering how reed petals should look, should they have all edges flush against the cage, or is a slight gap okay? Here's how they look now:

Lower reed is a bit loose, due for replacement? by mugget, on Flickr

Top reeds look good, just the lower ones that seem a bit loose. I guess that when the engine is running there will be internal pressure holding the reeds closed, but not sure what the service limit is, or whether it's a good idea to just replace them now while it's apart?

[2TInstitute]

flip them over

[JonW]

I think i have a set of Carbon Fibre reeds for a 380, not wanting a lot for em, drop me a PM with the sizes of yours and lets see if what I have fits your bike?

[mugget]

Genius!
Will flip 'em.

I thought I would take the cylinder to a shop & have it measured just to be sure & try to do things the "right way", but the guy there took a bit of a look at it and said that with the wear on the bore I should just go with the largest/D size piston as it wouldn't make much difference, no point in even measuring?

I forgot exactly what you mentioned on the phone Lozza, but I think you said pretty much the same thing? Since there isn't such a big difference between them?

Next question is just for my own info - but it looks like the bore to piston clearance should be in the range of 0.05-0.06mm (judging from what the manual says, although they don't mention the clearance, just a bore size & suggested piston 1 or 2/A or B piston). Is that correct, and is that just for cast pistons, would you have a bit more clearance for a forged piston?

Was hoping to find a piston kit on eBay, but most of them seem to be for standard/new bore as the pistons are 77.95mm. Or is that fine?

[2TInstitute]

Nicasil cylinders don't wear the piston does, the A,B,C sizes are just how they come out of the hone after the plating. Old mate has no fucking idea what he's on about. A .94 or .95 piston will be fine.

[mugget]

Okay, ordered a .95 piston and it finally arrived a couple of days ago. I was looking at the piston and...

Slight damage on the new piston... by mugget, on Flickr

Guessing that I should just file the rough edges down, hoping that it's not a big issue? But I'm not sure so just thought I would play it safe and ask...

Cheers

[2TInstitute]

will get covered up with carbon fast enough

[hybrid]

Yeah smooth it out if you want, especially if it protrudes towards the cylinder, but it's not a big deal.

[mugget]

I have everything out on the bench ready to reassemble... currently stuck on trying to install the new circlip into the new piston. Doing the first one while it's out on the workbench but it seems like a real bugger. Is there a special technique that I'm not aware of, or are they all just a PITA?

I saw one vide that showed inserting the open end of the clip into the groove at the opposite side to the notch, then placing the end of a screwdriver into the notch and popping the clip in that way. Maybe I'm just a bit hesitant because I haven't done this before, but seems like you gotta put a fair bit of force into it and I don't want to slip and gouge out the side of the piston or anything.

[hybrid]

I usually do what the video suggested. They do take some effort... you wouldn't want them popping out and destroying your engine. They really are pretty easy to put in. Just have a go, you'll be fine.

[2TInstitute]

Go down to JayCar and buy a set of their pointy little pliers that helps no end. There is no easy way unless the engine is on the bench, then lay the engine over. Make sure to put a rag under the piston and in the cases in case the clip does come flying off. Remember to turn the circlip end around to face away from the notch

[Jeram]

another trick is this.

put the clip in the hole at an angle so that is completely within the gudgeon pin hole, but just not lined up/straight. as it doesnt need inserting straight its a piece of cake

Then, using the old gudgeon pin (from the old piston), slide this down the hole and use it to drive the clip in straight and true

It should pop right in


PS: make sure to use a rag over the cases as lozza said

and don't forget to lube the small end bearing with little premix!