Should I attempt a 390 top end rebuild myself?

gjws · Nov 3, 2014

Hi all,

I've got 3100kms on my 390 at 110 hours. She is running well but after spending 3 days punishing her in 60 metre high sand dunes, pinned in 4th and 5th gear for hours on end, I'm seriously considering a top end rebuild. I try to do my servicing myself, in the past I have replaced all wheel, swingarm, pds and headstem bearings. I've inspected the valve clearance as well but have NEVER considered anything as ambitious as a top end rebuild. My question is simple, is this something that a non-mechanic should attempt? I'm happy to purchase all the necessary tools as I plan on keeping my bike for many years, so no trying to do things half *** with the wrong equipment.

Your thoughts would be very welcome, especially is you have performed a rebuild yourself and have some real world experience. Please, no one shooting from the hip with no experience, just saying "no mate, it's too hard". If you don't have a genuine understanding of what is involved, please refrain from posting.

Thank you!

Taffy · Nov 4, 2014

what is wrong with the top end? if the tappet check works OK then there is no wear.

it is that simple mate?

regards

Taffy

gjws · Nov 4, 2014

Hi Taffy,

I'm not aware of the tappet test so I'll have a search for it.

I have just finished a 3 day ride through Tasmania covering 550 kms. First, I dropped the bike during a river crossing. The water was filthy, so I'm worried that would have had an impact on the piston, rings and cylinder. I also had a little dirt fall in the cylinder while changing the plug, everything was super clean but some crap fell off the bottom of the tank when I was removing the old plug and I don't know how much went in.

My concern is I have a 7 day ride coming up in 3 months, and simply can't afford any trouble with the bike as we will be very isolated.

A stitch in time and all that

Taffy · Nov 4, 2014

for the dirt I would have spun the engine and then all will be good.
you can get these cameras now at the bigger engine reconditioners and large workshops. they will look inside.

nothing stays in a cylinder long - it gets outed on more or less the next stroke. the old yamaha WR400s ran a carb that used to lose a slide plate. none of the owner's new about it till the next halt when it would stall. the plates that were 50mm by 30mm had been sucked into the combustion chamber and outed. people didn't even know.

the tappet clearances can be done by any reputable workshop - especially if they have KTM experience as the top end is the same as the 530KTM motor.

I very much doubt that your bike is anything but perfect.

regards

Taffy

berglsmerg · Nov 4, 2014

Tappet clearances= valve clearances.

If it don't blow soot or feel tired I'd leave it.

The service manual is reasonably good but for a first time novice mechanic I'd at least try and have someone experienced working with me.

Idle · Nov 4, 2014

berglsmerg said:
Tappet clearances= valve clearances.

If it don't blow soot or feel tired I'd leave it.

The service manual is reasonably good but for a first time novice mechanic I'd at least try and have someone experienced working with me.

^^to make sure your t's are crossed and the i's are dotted....

you could prolly find some help here, or on DBW, or the AU regional forum on ADVrider.

you could do a top end if you wanted to, but i thimk its a little early.
At 250 hours you might be able to tell a difference, but its just broke in at this point.

ive got 477 hours on my 2005 650, same valves, rings, piston, lower end.

have a look at this thread to set your mind at ease:
http://husaberg.org/mechanical/15789-approx-fe570-miles-before-valves-top-end-rebuild-etc.html

gjws · Nov 4, 2014

Guys thank you all very much for the information, I feel much better about the bike now

I have done the valve clearance check before, so I'll do another one this week and see if things have moved at all. I have sand pretty much EVERYWHERE so I plan on stripping off the main tank, subframe tanks and radiators to give her a thorough clean. That should make access much easier.

Thanks again!

Should I attempt a 390 top end rebuild myself?

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