Strange compression issue and piston size Q

[Zakradu398]

MY compression a few months ago was 118 in my 400. Stock bore, stock piston. I was told under 105 you need to rebuild so I was good.

The other day I started leaking oil out of the rocker arm shaft washer so I tested compression again, same way, cranking it till the needle doesnt move with throttle wide open and it is reading 134 psi now. Why would it do this? I rechecked it about 10 times.

And also, what size piston is the next up from stock, I think a 406 or 407cc?

[dxcody]

Wiseco makes a piston that is a 85.5MM which is the next size over stock and that is a 402cc

Then an 86MM is a 407cc according to the wiseco site.


Not sure on the compression thing.

That is weird.

[Zakradu398]

After warmed up I am getting between 128-130psi.

I just adjusted my valves now, .005 intake and .006 exhaust but now it seems like it is smoking a lot more than before. Mostly on decel and rev limiter. I can actually smell it burning oil now.

[#484]

If your getting oil into the cylinder from a valve guide or past the rings it could raise the reading on a compression test. Let it sit over night and test again. if your compression is lower, squirt a very small amount of oil into the cylinder and retest. If the compression goes back up the rings are leaking and its time for an overbore and new piston. This is called a wet compression test.

[Zakradu398]

That could be it. Can i just pour a little oil through the spark plug hole?

And above I meant .004 intake and .005 exhaust.

Also, I let it warm up, adjusted the valves, let it idle for maybe 3 mins and took the valve covers back off to double check and there was a small amount of smoke or something coming out up there. I do have a bad washer on my rocker shafts, so it leaks a little oil from the head but that should'nt be the cause of it getting into the cylinder, should it?

Also, should I need it, is this the good gaskets by cometic? http://www.ebay.com/itm/Cometic-Top-End-Head-Gasket-Kit-HONDA-TRX-400EX-99-08-/290683298465?pt=Motors_ATV_Parts_Accessories&hash=item43ae1322a1&vxp=mtr

[CJM]

It sounds like oil might be leaking past the valves. The rocker area problem as well could be amplifying it. fix the rocker arm leak.

Yes you can pour it in the spark plug hole. In all honesty its time for a rebuild if its smoking. Do a 402 or 407 hi compression.

This is the kinda gasket you want-note it looks like rubberized metal. http://www.ebay.com/itm/cometic-top-end-gasket-kit-honda-trx400ex-400ex-c7825-/190518644764?pt=Motorcycles_Parts_Accessories&hash=item2c5bcbd01c&vxp=mtr

[on the rocks]

you should always adjust valves when the engine is at out side air temp. never let it warm up to adjust valves.

[Zakradu398]

Here's what I plan on buying

http://www.ebay.com/itm/Wiseco-PISTON-KIT-TRX-400EX-Oversize-86mm-040-w-11-1-Comp-Free-Frt-QPS-/380450750029?pt=Motors_ATV_Parts_Accessories&hash=item5894a1be4d&vxp=mtr

http://www.ebay.com/itm/TRX400EX-400EX-COMETIC-TOP-END-GASKET-KIT-99-08-STOCK-BORE-TO-86MM-C7279-/170839908390?pt=Motorcycles_Parts_Accessories&hash=item27c6da2026&vxp=mtr

http://www.ebay.com/itm/Hot-Cams-Stage-2-Cam-Camshaft-Honda-TRX-400EX-/390369400880?pt=Motors_ATV_Parts_Accessories&hash=item5ae3d45830&vxp=mtr


Along with a '05 crf 450 cam chain.

How do I fix the oil leaking past the valves or should I take it apart and take pictures to put them up?


I just ordered a Clymer also.

[HondaRacing83]

Sounds similar to what I'm doing this winter.

[#484]

Oil leaking past the valves will be fixed with new valve guide seals that are included in most gasket kits. Make sure you check the condition of the valves and springs while its apart, no time like the present to upgrade those parts as well !!!

[Zakradu398]

Well I just rechecked the compression and it is 95 psi. After a little oil in the cylinder it bumps up to 105-107. Guess I'll order a new piston now.

[Zakradu398]

My head cover is stuck on there good. What can I use to get it off without damaging it?

[Stickman400]

Tap on the sides with a rubber mallet.

[Zakradu398]

I dont have a rubber mallet but i used a piece of wood and a brass mallet. did nothing.

[Stickman400]

Put the piece of wood on top and hit it with a regular hammer a couple times then try hitting the sides. Try and break the gasket loose.

[Zakradu398]

I got the front part to come up about 3-5mm but the back is stuck on

[Stickman400]

If you can pry it off do it, it's just the gasket holding it together. Just make sure you don't gouge the gasket surface when you're prying on it.

[Zakradu398]

I dont know what to pry it with without hurting the surface.

[CJM]

Just pat a rag over the screwdriver and pry.

I smack my valve cover and the head with a 16oz ball peen CAREFULLY. Aint busted it yet.

Or you could buy a rubber mallet...

[Zakradu398]

I got a rubber mallet off my dad. I mananged to pry all the sides up like 2mm but it still isn't coming off. Not even close.

[CJM]

You sure you got all the bolts out?

[Zakradu398]

12 of them

[jgar]

I think there is 13 bolts. If I remember correct there is 1 in the middle by the mount.

[Zakradu398]

dumbass me, there is 13. The manual said 12 6mm bolts. and theres 12 8mm and 1 12mm. Whats up with that? I may have damaged my valve cover... i think the head is fine though.

There are just small gouges can I use gasket sealer for those areas?

[hocman123]

the thread size is the number they talk about in the manual not the head size. and it says 12 6mm bolt and one 8mm bolt.

the seals sould be fine unless the gouges are really bad i wouldnt bother with the sealer

[Zakradu398]

How does everything look? And are those colors on my connecting rod ok? Crank has a blue tint all over, Cylinder looks great though, no marks/scrapes/nicks anything. Crosshatching still slightly visible.

http://i148.photobucket.com/albums/s31/zakrad_u/datFOhundy/DSC_0503.jpg
http://i148.photobucket.com/albums/s31/zakrad_u/datFOhundy/DSC_0502.jpg
http://i148.photobucket.com/albums/s31/zakrad_u/datFOhundy/DSC_0501.jpg
http://i148.photobucket.com/albums/s31/zakrad_u/datFOhundy/DSC_0500.jpg
http://i148.photobucket.com/albums/s31/zakrad_u/datFOhundy/DSC_0499.jpg
http://i148.photobucket.com/albums/s31/zakrad_u/datFOhundy/DSC_0495.jpg

[Stickman400]

Looks pretty normal, the bluing on the rod is normal too. The head and piston look really wet in the pic for some reason. Is that 2nd to last pic the valve cover or the head? That looks pretty gnarly. You may want to smear just a dab of sealant on that spot before installing the gasket, unless you want to take a chance that it may leak once you get it back together and you have to take it apart again.

[Zakradu398]

Its wet because I had a little oil in the cylinder to test comp. and that's the valve cover.

How can I clean the carbon off the head?

[CJM]

Take a wire wheel to it.

Since your going to be doing valve seals you might as well lap the valves as well. Get valve grinding compound and smear it on the bottom of the valve head. Then take a drill and chuck the valve in it in the head and spin it moderately. Your actually sanding the valve/head area. Then brake cleen it all off and your done.

[Zakradu398]

Can I wire wheel it with the valves in there? And I'm not sure I understand the lapping. Can you give me a link to the compound also?

If this stays cheap, I'll snag it up for added assurance unless you don't think I need to?

http://www.ebay.com/itm/330762429463?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649

[CJM]

Heres what I would do. Take a dremel, file or similar and smooth out the valve cover-if you cant find one cheap.

Valve grinding compound (http://www.amazon.com/Permatex-80037-Valve-Grinding-Compound/dp/B000HBM80M)

lapping valves (http://www.myhonda650.com/cb650lapping.htm)

Do exactly as the link says but chuck the valve into a drill and go to town (keep the rpms down). You dont have to go insane, just about 10 secs in each direction. Using a drill is 100X easier than those suction cups.

[Zakradu398]

Damn CJM, thanks for all the help so far. I'm sure I'll need more :p