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

[mugget]

Bahaha... I must be a slow learner.
I'm sure it will sink in eventually!

[2TInstitute]

Break in method in the 2 stroke GP world was this. 2 laps at 3/4 pace ride through pit lane and out again DONE.

Remember as Spanky said "nobody ever killed a 2 stroke with too much oil "

[mugget]

Okay gurus... I have done the leak down test three times and it's giving me serious grief!

First up after I tightened my frankenstein tester & fixed it's own leaks, there was big pressure loss from the power valve/exhaust control cover.



Removed the little PV side covers, removed the exhaust control cover, cleaned all the silicone off. Reapplied more liberal amounts of silicone, bolted it up & next test that is fine. I could see where there is a bit of space at the top where the silicone was thicker. Fair enough, won't make that mistake again.



But then found a leak at one of the PV side covers.



Okay, no worries... it's just a gasket, I'll add some silicone and fix that up. Done. Then 3rd test, it's still losing pressure - from 5psi it drops to 3psi in 13 seconds, down to 2psi in another 7 seconds and 1psi in another 16 seconds. Except this one looks like it's coming from the rear of the cylinder base gasket right in the middle...



I don't know what to do now, can't just fix that one with silicone, right? Looks like I'll need to buy some better gaskets, these ones were Moose I think. And then redo all the X and Z dimensions. Bugger. But better to get it all sealed up tight rather than trying to do a dodgy fix...

Or maybe I should rig up a spanner to the torque wrench to check the cylinder base bolts are tightened to spec first? Might just be leaking because they're a bit loose? Or not? I tightened them as tight as I could by hand, without bolting the engine down and swinging on it like an ape.

[2TInstitute]

threebond both sides of the gasket

[mugget]

Cheers for the ThreeBond tip! I did have some kicking around my tool box as well, forgot about it. Bought a genuine base gasket & cylinder side gaskets, ThreeBond applied and zero leaks!

Some may get a laugh from my Frankenstein leak tester.


The engine is in the frame now, just about ready to roll... but I'm a bit stuck on the wiring. Here's the schematic per KTM manual:


The part I don't understand is that it shows 4 wires to the capacitor positive terminal (#19). I'm also not sure how to read "ge-r", whether that is 1x yellow and 1x red wire, or 2x yellow with red tracer? In any case the capacitor takes those screw down type connectors, and there's not many on the wiring harness. All of them are shown in this photo:



I'm not using a battery, so they can just sit to the side. The ground - can I attach that under the bolt holding the rectifier? Or under the coil? Does it matter?

I just wanted to check if anyone could make more sense of this than I've been able to... and I don't want to just connect it how I think it should go if it's going to risk frying something when I start it up?

Also I can't see a fuse anywhere in the wiring - should I add one in? Just to be sure?

EDIT >>

Bonus question Re: reed stop plate


I posted this photo earlier asking about that gap between the lower reeds (flipped them over so there's no gap now) but was looking at the fiche diagrams and noticed that it shows a "reed stop plate"? On all of the model variations except the 250 SX?? And reading a jetting article I noticed it said not to remove the stop plates, "There is no more power to be had, just broken reeds".

So what is the story - no issue? Or a definite no-no to run without the stop plate? Or passable if you regularly check the reeds for wear?

And feel free to tell me if I'm overthinking it again...

[hybrid]

The plate is there to stop the reeds opening too far (past their safe bend angle) and snapping.
If your bike is meant to have one, you should use it. You did the right thing by flipping the reeds.

Can't help you with the wiring, except that yes, the "colour1-colour2" in most wiring diagrams means colour1 wire with colour2 trace.

[mugget]

Okay, got everything bolted up. I've been kinda nervous about the first start, so I've been delaying a bit... Took it outside for some photos today and thought I'd just give it a few kicks and see what happens.

Didn't check anything (spark etc.) prior to this, assuming the start key has been bypassed... but I found fuel leaking from the tap and the carb bowl as well, been so long since I started this project I probably loosened the bowl to clean it out and forgot about it! So I didn't put too much into getting it started, but now I'll run through all the usual things and see what's going on.

Anyways - here's how it's looking at the moment:

KTM 380 SM JDMxKTM 2 by Mugget, on Flickr

KTM 380 SM JDMxKTM 1 by Mugget, on Flickr

KTM 380 SM JDMxKTM 3 by Mugget, on Flickr

KTM 380 SM JDMxKTM 4 by Mugget, on Flickr

Rear wheel is a tight fit, still not 100% sure on chain/sprocket alignment so I've gotta check it out. The pipe looks mega from the front. And not used to KTM/dirt bike chain tension, think I need a bit more slack in there.

Anyway I've got a new carb bowl seal now - the bowl actually looks really clean, so I'll just check the needles/jets and put it back together. Hopefully spark is good and I'll get a video of it running soon!

[JonW]

Ohhhh Gi'usago?! Looks great!

[hybrid]

Looks fantastic mate!

[mugget]

Okay fellas!

So I have the bike all back together. I gave it some kicks to see what would happen and all I got out of it was a backfire. I hadn't checked spark, fuel etc. at this stage - so I took off the carb and cleaned it out, looked like there was a bit of something blocking one of the passages.

Just now I've got a chance to check for spark - and nothing. New plug as well.

So I'm wondering if I plugged something wrong with the wiring? Or if there's something else I should check?

First ride is so close now!!

[2TInstitute]

did you paint the frame? If yes you might be covering a earthing point, you might have to take any earth points back to bare metal

[mugget]

Yeah, the frame was freshly powder coated. I did sand bad the frame tab where it's grounded, pretty sure I got that right, will double check it.

Someone else said that you have to actually give it a good kick to create spark? It won't do if you just take the spark plug out and crank the start lever by hand?

[hybrid]

Not sure what kind of ignition it is. I assume CDI.
You should generally get a spark out of it with the plug out and pushing the lever even with your arm.
The stator will charge the cdi, so it does need to spin fast enough to create that charge.

[mugget]

I mustn't have been spinning it fast enough with my arm. Got someone else to look at the plug while I was sitting on the bike giving it a proper kick. 100% there is spark! So not as chronic as I thought...

Have spark, carb is clean - just gotta see if I can get it started next bit of free time I get!

[mugget]

Aye aye maties!


Well, what an update I have for you...

I finally got sick of the bike sitting in the garage not running. Other more important work-related projects came up, so I wasn't going to look at it anytime soon. Took it to the shop, just wanted to have it running!

Well it turns out I really buggered up when I put the head back on, there was an o-ring missing, apparently! WTF?? I cannot believe I would do that, but anyway... they also said the base gasket was on upside down but that shouldn't have caused any problems. There was coolant in the cylinder, which wouldn't help.

They cleaned that up and also looked at the flywheel, woodruff keys etc. All good no problems with the engine. They cleaned some dirty connections and got a good strong spark.

The problem is - the engine has some crazy compression. I should get them to measure it, they did have it running & idling, but didn't ride it. They had to get the biggest guy in the shop to kick it, and he did it so much that it warmed up the engine just from that! Then they still had to use AeroStart to get it started.

Next day, cold start - not a chance.

So it looks like I just need to get the head modded again to reduce compression??

The head was modded down to 1.3mm squish (as mentioned previously in this thread), but just the squish, no chamber reshaping etc. Would that a make a difference? I'm going to get it out of the shop now anyway, already racked up a workshop bill of $847...

I am thinking I will just take the head to the local engineering shop and get them to reshape the combustion chamber and machine the squish out to a larger measurement - but not sure what? 1.8mm? 2mm? Or do you think it could be some other problem that they're not thinking of, I didn't think that the head mod would affect it so adversely? Awaiting your knowledgeable responses!