removing crank case 3

13 replies to this topic
  • brianO1YZ426

Posted March 02, 2008 - 10:53 PM


i am about to remove the crank case on a 426 and i was wondering if anyone has any pointers for me. I bought the bike with a striped oil cover hole and am going to take it to a machine shop to get fixed. is this a quick and easy thing to do, or are there lots of things that can go wrong? do i need to cover the engine while its off? are there many items inside i need to keep track of? will a person with almost no knowledge on a 426 screw himself trying to do it himself? any advice would help :smirk:

  • USED YZ426F

Posted March 03, 2008 - 06:04 AM


1) First things first, get yourself a service manual if you don't already have one. There are links in the sticky threads to them.
2) The repair you want done is not that hard to do and shouldn't take a good machine shop more than a half hour or so to complete.
Have you considered doing the work yourself? I think that you may be able to install a helicoil without taking the side case off,not completely sure though. Would someone with more knowledge correct my thoughts if wrong?
3) You should definitely cover the open engine to protect it from dirt and other debris until you get the cover back on.
4) Does almost no knowledge of a 426 also mean almost no knowledge of an engine? All engines are very similar, and a good shop manual will point out any differences that you need to be aware of (see #1). If you are mechanically inclined, you should be able to do the work yourself and save a few $.

Just my .02 cents.

  • tnl

Posted March 03, 2008 - 06:42 AM


Timesert should be all you need: Shouldn't need to split the case for your problem?

  • grayracer513

Posted March 03, 2008 - 07:42 AM


When you say "crankcase", are you sure that's the right term? The crankcases are the two main engine cases at the center that house the crank and transmission, and carry the cylinder and head. "Splitting" the crankcases involves th ecomplete removal and disassembly of the engine.

I'll assume that you are talking about one or the other of the two crankcase covers, then?

  • brianO1YZ426

Posted March 03, 2008 - 01:15 PM


yes gray i am talking about crank cover #3 in the parts book its 200 buck if that helps. btw about the timesert... the machine shop said, "that is a last effort", to do the helicoil first. Should i tell him i want a timesert or nothing or take his word for it (also he said he wants me to take the case off or pay more for them to take it off). I have worked on KDX's before, i had one from the time I was 12 to about 15 and did most of the work with my dad so i know some things about moto engines but not a pro at all. if you want to know exactly what part is stripped the address to the page is http://oem.thumperta...casecover1.aspx its part #10

  • grayracer513

Posted March 03, 2008 - 01:44 PM


Right side crankcase cover. Which hole is damaged?

  • brianO1YZ426

Posted March 03, 2008 - 01:49 PM


bottom oil cover hole where the hex screw goes in. you have posted about this one in your comm. faq section.

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  • grayracer513

Posted March 03, 2008 - 02:08 PM


A Time-Sert is a better repair than a Heli-Coil for threaded holes such as this that receive repeated use.

Before removing the cover, be sure to drain the oil and coolant. Remove the water pump impeller cover so you can turn the impeller by hand to align it on the way back together. Read the manual. Not too tough.

  • brianO1YZ426

Posted March 03, 2008 - 02:15 PM


thanks man ill call this guy now and tell him i prefer the timesert and ill be sure to drain the oil and coolant

  • USED YZ426F

Posted March 03, 2008 - 04:11 PM


Just curious, but did the machine shop recommend doing something other than the helicoil or timesert? How much are they going to charge you for the repair?

  • brianO1YZ426

Posted March 03, 2008 - 06:50 PM


no just a heli coil and he said about 40-50 bucks

  • USED YZ426F

Posted March 04, 2008 - 04:53 AM


no just a heli coil and he said about 40-50 bucks

You can do the work yourself for a fraction of that cost if you own a drill and a set of bits. If you don't, well then borrow from a friend or neighbor.

Helicoils and timeserts are both easy to install. Should only take about 20-30 minutes to do (sounds like he was going to charge about 30 minutes of shop labor).

Just my .02 cents.

  • brianO1YZ426

Posted March 04, 2008 - 01:37 PM


well im looking at time serts and there 60 bucks so is it worth me trying to do it my self?

  • grayracer513

Posted March 04, 2008 - 02:45 PM


They are a significantly better repair for this kind of thing than Heli-Coils are, and IMO, they are easier to install correctly, especially in smaller sizes like the 6mm we have here. Especially if you haven't done a Heli-Coil before.

If you are good with hand and power tools, and can follow instructions, you should be able to do it. The kit should come with several inserts. Install one in a piece of scrap aluminum for the practice.

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