Engine Noise / Runs harsh after 3/4 throttle

[MisterGraphic]

Alright Guys,

I put my 4wheeler back together and I'm having trouble finding my problem.
It makes a loud ticking noise (hot cam stage 2) but it doesn't run well after 3/4 throttle. (Under load it is worst)
I thought it may have been predetonation, so I put in a bigger main jet.
I re-ajusted my valves to Hotcam's specs and replaced my spark plug.

Went to try it out and it still does it.

I found a video (not mine) but it sounds exactly like that when idling.
http://www.youtube.com/watch?v=d6QeRQ8QuNw&feature=player_embedded#at=13

Tomorrow I'm removing the valve cover and making sure the timing is correct.
Double check to make sure the cam chain isn't stretched.

While I'm doing that, is there anything else I shoud do ? Any suggestions ?

[honda400ex2003]

why would you think that jetting up would stop predetonation? im just curious... jetting has no effect~ higher octane does. if you suspect predetonation, go up a gas grade and jet it back to where jetting is correct. at least 91 if not 93. some cant even get away with that if you are really running it hard esp with the heat of a 426.

steve

[CJM]

Start by upping to 93 if you arent already using it.

Then check the plug-what does it look like-lean, rich, burnt, etc.

[tri5ron]

Ok, first give us some background to better understand what's going on.
You say that you just got your bike back together.

What exactally does that mean?
What was it doing,(or not doing), in the first place, to cause you to take it apart ?
Was it running poorly?
What did you do to it?, and what did you change ?
Did it already have the stage 2 cam, or is that a new install that you did?
How about the 426 / 11:1 set-up, is that something new too? or was it already in the bike before you took it apart ?

Is there any indication of oil leaks at the head gasket?
Does the bike have HD studs installed?

Did you do all the work yourself?

[MisterGraphic]

Thanks for the replies,

First off, I read online that running lean could cause predetonation. I am not a mechanic so don't ask me to explain it.
I knew about the Octane so I've been running Premium.

I have never heard or felt predonation so I don't know what I'm looking for.

What I did :
Bike was stock and burning oil. Was running good though.

I opened the motor and did this myself.
- Had HD studs installed
- Got the motor bored to 426cc
- Installed a Stage 2 hot cam
- Torqued everything to spec
- Cometic Gaskets
- Adjusted the valves (first at stock specs, then at HotCam's specs)
- Full Sparks exhaust
- Uni Air filter (oiled...obviously)

Broke the motor in with conventional oil. ( 2 changes of conventional oil)
Notice some clutch slipping so I replaced the clutch.
So the bike starts well and idle well. I went for a drive and it worked very good.
My second drive I started feeling that "noise/loss of power" when underload at the upper end of the throttle.

There is nothing leaking around the head so I'm hoping it's not the gasket.
Could timing chain stretch cause it to lose a lot of power when on the throttle ? It's really the only thing left to re-check.

What do you guys think of the video I posted ? (not mine, but similar sound)

[MisterGraphic]

From reading this description / comment,
maybe it could be predetonation, but I'm unsure. I didn't want to try it over
and over because the sound wasn't too pleasing and didn't sound "healthy" at all.

http://www.thumpertalk.com/forum/archive/index.php/t-851903.html

[tri5ron]

ok, it's great that you are trying to learn your bike and do your own work. That's a good thing. You say you are not a mechanic, but it also seems like you have done some of your homework, and have tried to cover your bases.
In light of that, I'm a little confussed as to why you would do an entire top end rebuild/upgrade, and not upgrade the timing chain and tensioners at the same time. it's one of the most common things discussed here on the forum.... But it is, what it is, and now we need to help you figure out what to do.

SO,...
Understanding that it is difficult for us to perscribe or suggest without actually being there,... and not having seen what you did during your build,... we'll give it our best shot.

First, you have to realize that 400EX have a notorious history of ticking even when stock.
Second, the Hotcam stage 2 makes it even worse. It's possible that you are just not use to the sound yet.

Listening to a video of a different bike does no good. yeah, ok, you say it is similar,... but the reality is, that it's not your actual bike, and who's to say what your description of "Similar", and anyone elses description is the same?. so, that doesn't really work for me.

Personally, if it was me,... I'd start with replacing the timing chain and tensioner, with the CRF chain.
I would want to know in my own heart, that the chain is as strong as the rest of my new build.
Remember,... if that chain lets go, it will basically ruin your engine, and waste all of the hard earned cash, and time you just put into it. (look at the recent threads over the past couple of weeks, reguarding timing chains gone bad). It's just not worth taking the chance, .....especially with a higher lift cam.

Make certain that it is done correctly, and ask someone with experience to assist you, and to double check your work.
There is no shame in that, and you are still doing the work, learning the rights, and wrongs, and doing so without all the guessingor assuming that you may have.
Don't be afraid or embarrased to have someone there with you.

Once you have ruled out the possibility of the chain/tensioner,...
and you have confidence that everything else is verified correct,..
Then you will know that it is the new sounds of your new build w the bigger cam. and your throttle problem just may have gone away at the same time.

If it has not, then it's most probably down to a jetting issue.

btw,
who did the bore/hone job ?
and did they have your new piston in hand PRIOR to doing the honing ? or did you tell them what to bore it to, while you were waiting to recieve the new piston ?
Also,
How did you verify the correct direction, to install the piston rings?

Did you use a manual during your build ? and where did you get your torque specs from ?

Did you have GTT do your HD stud installation ?, or was it a shop local to you ?

I'm confident that some of the more experienced members than myself, will also chime in to help you. they may also have some other questions that I have forgotten to ask.

Hang in there, it'll all come together.
It should be a nice solid build , and strong running machine, when you get it all done.

Good luck.

[MisterGraphic]

Thanks for the reply,

Local shop installed the studs with instruction supplied by GT Thunder.
Cylinder was honed by the same engine shop and they had the piston on hand to get the proper measurements.

They installed the ring and I made sure the gaps were not aligned when I installed the cylinder on the base/over the piston.

My guides and chain looked brand new and I didn't notice any slack in the chain.
I'll take the valve cover off to inspect before doing anything else.

Live an learn I guess.
Oh and I did the entire work following the Clymer's manual.

[MisterGraphic]

Found my problem.
Took the valve cover off and the screws holding
the top cam sprockets were about to come off.

Good thing I didn't run it more....
I don't really understand how they would have
come undone since I used locktight on both of them.

That causes a new problem since the loose bolts
stripped the threads in my brand new Stage 2 hotcam.

:s

[CJM]

That really stinks!

Just use the gear from the stock cam, Im not 100% sure but I dont think it matters.

[MisterGraphic]

tomorrow I'll be removing the head/cylinder to replace the timing chain guides.

Should I replace my (literally new) cometic gaskets while I'm there ?

I'm assuming i have too, but wanted to verify before I order a new set.

Concerning my cam, there's not enough room to re-tap the holes so I'll be buying a new one....
I'm still waiting for a reply from HotCams in case they can send me a new "butterfly" to hold
the sprocket on the cam....A local machine shop told me they could press a new one in.... (kinda skeptical about that)

[CJM]

Sure you can press one on, thats all they are to begin with.

All gaskets can be reused except the base gasket iirc. Thats the only one made of paper