Engine Gurus, please help me!!!

[stng_96]

Ok guys, here is the story, I bought my 400ex, with a blown headgasket. It already had the 426 kit in it, and I ported the head, and added an aftermarket cam the previous owner gave me. I dont know anything about the cam, only that when I measured it, it is in fact different then the one that was in the bike, so I am confident it is aftermarket. Also, my bike has the 11:1 wiseco kit in it. So here is my problem....

I got it all finally together today, all is well and good, timed it according to the manual using the "T" mark in the timing window, along with the marks on the cam gear. Set the valve lash to factory specs, and started her up. Tick Tick Tick.....

Ended up pulling it back apart to find that the intake valves were slapping the piston. Now luckily there was no real damage to either the valves or the piston, so as per a buddies suggestion, I retarded the cam by on tooth on the gear, tried again, and it still slaps. It is not as bad now...but it still does make the same sound, and I really don't know if it is now the intake or exhaust.

Anyways, what I am wondering is if there is anything special I need to be doing to make this setup work. I know I am not the first one in the world to try this....so please, I am begging for suggestions.

Also, sorry for the long read, I just wanted to cover all the bases to eliminate questions.

[Pipeless416]

are you sure the piston is in facing the right direction?

[jcs003]

Originally posted by Pipeless416
are you sure the piston is in facing the right direction?

x2

[CJM]

The pistons probably backwards-should be an arrow that faces the front of the bike. I would try some looser tolerances for the valve lash of .006 exhaust and .005 intake just to see.

Also when adjusting the valves its crucial that everything really is in time. Just cause the mark is there doesnt mean its at true TDC. You gotta grab the rockers and make sure they are a little loose-if not its not truly at TDC.

[stng_96]

Yeah, I considered that option after I got it back together this time....because I never really did check to see if he got it in there straight.

[stng_96]

Ok, I just pulled the head again, it the piston is in correctly(arrow facing front). Also, I did try to change the valve lash a little, and it didn't help.

[CJM]

Are you 100% sure the valves are hitting the piston and its just not the tick all 400exs tend to make?

Some can tick rather loudly.

[Pipeless416]

Originally posted by CJM
Are you 100% sure the valves are hitting the piston and its just not the tick all 400exs tend to make?

Some can tick rather loudly.

yea, to be sure you should try turning it over by hand using a wrench on the crank. also, you could clay the piston and see what clearance you're getting.. last, your cam is being installed with the lobes down, correct?

[dustin_j]

Originally posted by CJM
The pistons probably backwards-should be an arrow that faces the front of the bike. I would try some looser tolerances for the valve lash of .006 exhaust and .005 intake just to see.

Also when adjusting the valves its crucial that everything really is in time. Just cause the mark is there doesnt mean its at true TDC. You gotta grab the rockers and make sure they are a little loose-if not its not truly at TDC.

This is a good post. I just want to add, are you checking timing after you release the tensioner? Since the cam chain tensioner only acts on one side, it will rotate the cam slighly as it tightens. When installing a new and especially an unknown cam, take pipeless' advice and clay the piston to determine clearances before running. If the valves did contact the piston, be sure to check for binding and cracks before using.

[Dirtdog400]

You really need to find out more about the cam. Also, is it possible the head could have been machined by previous owner and therefore making the valves contact the piston?

[CJM]

fyi turn counter clockwise too, not clockwise!

[togup]

The exhaust gaskets are a common culprit for ticking as well

[stng_96]

So, just got back from thanksgiving break, planning on claying the piston this week. Timing is spot on, and cam lobes are down. I had already decided to clay it now because I I can turn it over with the wrench, and I am wondering if the valves actually are still hitting.

[AtvKid4Eva]

chances are that if you bought it with a blown head gasket that it needs HD head studs to keep the head gasket from blowing..it might seem ok now but when you put some hours on it its gonna blow again with the stock studs, since it has happened once. ive seen it on so many 400's. as for the ticking make sure you are adjusting the valves correctly if they are too loose or tight they will tick and if its a Hotcam which is likely then they are pretty loud which is normal. i doubt the tick is from the piston hitting the valves. also make sure the tick isnt from air coming through the head gasket. good luck man.

[killer454]

i bought a blownup 400ex and redid the piston and rings and bored the cylinder .020 ran fine after all that but foundout the timeing chain tensioner was bad causing the chain to slap.this was bad with the previous owner and he did not know it was or did not tell me.

make sure you check the tensioner real good!

[stng_96]

I already put in HD headstuds, thats not the issue, and I converted the tensioner to a manual one, so I know its good, the only thing I have not done is replace the timing chain, which is being ordered today.

[CJM]

You want a chain from a CRF450 approx 00-02 iirc. Thicker and stronger.

[jensenracing77]

Originally posted by CJM
You want a chain from a CRF450 approx 00-02 iirc. Thicker and stronger.
and cheeper also
the TRX 450ER also (06 and newer)

[Thumpin440ex]

Some good points made here.. Clay the piston, to valves to see if it is making contact.. Be sure that the previous guy didn't have the head machined, to raise the comp.. Can you see any physical marks that the piston is hitting the valves?? I mean if all is in correct, timed, spec'd, that would be the last real culprit.. I know after I did my 440 kit, with cam, head work, it def has a more distinct tap..
Let us know when you fig it out..

John

[stng_96]

Yeah, I was planning on the 02-08 crf450 chain, no reason to do another stocker, but I hadn't heard about the 450er chain, is it the same as the crf?

I can actually see marks on the valves/piston from where there was contact, but it is extremely minimal, as in the paint from the paint pen I used to mark the valves when I took the head apart has not even worn off. I am the same as you thumpin, I really only think at this point it could be the chain, as I am not novice to this kind of thing, and I followed the manual to the T when putting it back together. Timing was dead on, valve lash dead on, so I really don't know what else it could be. also, the head shows no signs of machining, so I doubt it was that.

Ill let you guys know

[stng_96]

Alright kids, got my 08 CRF450 chain in, clayed the piston, and all looked well. There isn't much clearance, but its definitely not hitting anymore. Words don't even describe how much tighter this chain is then my old one was. That being said, with the performance cam in there now( which my buddy says is a hotcams), the ticking is down considerably, down to what I believe is just the cam.

Havent ran it much yet, but just enough to know that I think I am good to go now. Tommorow Ill actually get it out and ride it a bit.

Thanks for the suggestions guys