PDA

View Full Version : How to tips for boring & resleeving your 400ex



Dunlap
12-08-2003, 06:59 PM
This by far has been the biggest headache for most 400EX owners. I have read so many posts on here about blown head gaskets, I would like to give a few tips on what I have seen and what I have done here at Four Stroke Tech to eliminate head gaskets problems after boring or re-sleeving the 400EX.

After you remove your cylinder, the first thing to do is to find out if your cylinder is any good and if the studs have either come loose or are pulling out of the cylinder. Before you do anything, torque the studs by putting 2 nuts together (stock 400EX nuts off your wheels) back to back work good. The cylinder studs should be torqued anywhere from 35 to 40 foot pounds. If they won't hold this, your studs are pulling the threads out of the cylinder. If they don't hold, you can either go from a 10mm stud (which is stock) up to a 12mm after-market stud and re-tap your cylinder. I have had great success with using Time-Certs which is a heavy-duty helicoil. If your cylinder holds the torque then go ahead and remove them and if you are just boring your cylinder, clean the studs and the threads in the cylinder with acetone (or some kind of de-greaser). I use Honda high-temp lock tight liberally on both the stud threads and the threads in the cylinder re-installing them and torquing them to spec. After this, go ahead and bore your cylinder to spec.

http://www.imagestation.com/picture/sraid92/p977af3cfc4c27108bb1943b5594cd449/fa59c39e.jpg

Dunlap
12-08-2003, 07:12 PM
If you are re-sleeving your cylinder, leave the studs out. Measure your sleeve while it is room temperature and bore your cylinder so it has at least a .005 interference fit. If the sleeve is not tight enough, it can work up and down from the friction of the piston and cause your sleeve to drop. Also, it will draw oil up between the cylinder and the sleeve and will not properly transfer the heat out of the sleeve through the cylinder. It is important to hone the cylinder to its final spec before installing the sleeve to help with the heat transfer and to eliminate hot spots. Heat your cylinder either on a hot plate or in the oven for about 30 minutes getting the temperature up to 150 to 200 degrees before installing the sleeve. Once you have installed the sleeve, it is important to hold it under pressure in a press to keep the sleeve from raising out of the cylinder. I leave the sleeve .002 to .005 higher than the deck to help bite into the head gasket for a better seal or in my 500 kits we use a stainless steel O-ring which has a thinner surface area and can bite even harder into the head gasket.

http://www.imagestation.com/picture/sraid92/pea907e950f04e32ba895ee661f169410/fa59c393.jpg http://www.imagestation.com/picture/sraid92/p9ddc58fed4e75d620068979e59bac3cb/fa59bb14.jpg

416mx
12-08-2003, 07:12 PM
Have you ever had or herd of any problem with broken sleves after boing cyl to a 426, sinch this is the last bore on a stock cyl is the wall of the cyl too thin?
I'm debateing over a 426 or resleving and going to a 440. It's a 416 now.
Thanks

Dunlap
12-08-2003, 07:21 PM
After it has cooled re-install the studs cleaning them and the cylinder using acetone. Lock tight and torque them to specs. The reason we install the studs and then bore the cylinder is because there is a bulge at the top of the threads that go into the cylinder that pushes the aluminum into the steel sleeve and pinches it. You may not see any difference in your cylinder after boring it but once you ride the machine and if you have installed the cylinder studs after you bored it, you will get 4 tight spots where the studs have been tightened down after boring.

http://www.imagestation.com/picture/sraid92/pa3f89eadd560de6833bfd3619ac83223/fa59c398.jpg

Dunlap
12-08-2003, 07:32 PM
On most 440 kits the sleeve will be hanging into the dowl pin area and you may need to grind the sleeve slightly so your dowl pins fit securely. Once you are re-installed the studs, then bore your cylinder to spec (which is usually .002 to .004 on most after-market pistons). One other thing to watch with the 440 sleeves is about 80% of the 400EX I have worked on the cylinder sleeve touches the cases where it goes down into the cases right in the back between the 2 case halves. A way to check for this, is to remove your dowl pins from the cases, set your cylinder down into the hole and try to move it front to back. It should have about .020 clearance front to back. If it doesn't, you will need to grind the cases to give it clearance. Otherwise, the cases will push into the cylinder sleeve and cause a hot spot at bottom dead center with your piston which will lead to your cylinder cracking or your piston scuffing - or both. A good way to keep the metal shavings out of your bottom end if you have to grind it is to stuff paper towels down around your rod and crank and then fill about 1" layer of spray foam insulation (Neat Stuff) on top of the paper towels. When you are done grinding, you can vaccum all the metal out, pull the insulation out and then the paper towels. I hope this helps you with your next big bore kit.

http://www.imagestation.com/picture/sraid92/pd6cb13ab01e3a64550f9555e400f5a8c/fa59bb18.jpg

Dunlap
12-08-2003, 07:34 PM
Originally posted by 416mx
Have you ever had or herd of any problem with broken sleves after boing cyl to a 426, sinch this is the last bore on a stock cyl is the wall of the cyl too thin?
I'm debateing over a 426 or resleving and going to a 440. It's a 416 now.
Thanks

I have built a few 426 motors with no problems just boring them in .

JOEX
12-08-2003, 07:37 PM
Thanks Mickey! It's great to hear some 'tricks of the trade' from the pros:)

Joe

pnut420
12-08-2003, 07:52 PM
Thanks alot Micky, that must have taken some time to write that up, I'll read it over and over again, good to see you on this site and thanks for the help. :cool:

Dave400ex
12-08-2003, 07:57 PM
There was some great information there. Very good tips. Thanks a lot Mickey.

Silverfox@C&DRacing
12-08-2003, 10:38 PM
Originally posted by 416mx
Have you ever had or herd of any problem with broken sleves after boing cyl to a 426, sinch this is the last bore on a stock cyl is the wall of the cyl too thin?
I'm debateing over a 426 or resleving and going to a 440. It's a 416 now.
Thanks

if you are worried about this you can put a ross sleeve in and still be a 426 and that sleeve can be bored to a 440 also.

hawiianpwr
12-08-2003, 11:16 PM
Yeah thats some nice info that should go into the maintenance forumn:)

Dunlap
12-09-2003, 09:50 AM
Glad to help, I hate to see so many people having problems with high performance parts on there 4-stroke because they got a 4-stroke for reliability in the first place. There should not be any reason you cant have killer power and reliability just like my 500cc kits.

http://www.imagestation.com/picture/sraid92/p12256cb0ca20d7fba85726313966391b/fa583862.jpg

To get any real power you must go inside.