Mystery part in Head

[Knips178]

I just got a head from someone off ebay and in the box with the head was a little semi hollowed out rod about 3/4" long and 1/8" thick and spring that looks like it goes around it. anyone know what that is? i also have pic of it

http://domino.newvisionnet.com/Joey/atv/March%202004/P3230041.JPG

it's on the right side of the head by the washers.

[RAFFERTY1]

it could be the oil passage which sits in the head under the camshaft.

[y2k400ex]

thats the plunger and spring for the de-comperssor for the cam.

items 4 and 5
http://www.servicehonda.com/hard%20parts/atv/trx400ex/cylinder_head.htm

[Doibugu2]

Originally posted by y2k400ex
thats the plunger and spring for the de-comperssor for the cam.

yep

Aren't you using a manual, I know it talks about that peice.

[UglyMotha™]

Originally posted by Doibugu2
yep



yep

[foleyit]

Originally posted by y2k400ex
thats the plunger and spring for the de-comperssor for the cam.

items 4 and 5
http://www.servicehonda.com/hard%20parts/atv/trx400ex/cylinder_head.htm


Yep, its the plunger and the spring for de-compressor for the cam. Keep in mind if you are going to be running an aftermarket cam (Hotcams) -- they DON'T require those two items.

[Knips178]

That's just what I needed to know. I am getting a hotcam so I can just set that plunger and spring aside. Just out of curiousity, if that plunger and spring wasn't in there, would the quad run?

[UglyMotha™]

Originally posted by Knips178
That's just what I needed to know. I am getting a hotcam so I can just set that plunger and spring aside. Just out of curiousity, if that plunger and spring wasn't in there, would the quad run?




i havn't had mine in for a year and it still running


the spring and plunger is only there to engage the decompression unit on the stock cam for ease of starter most aftermarket cams does not use this mechinism and if you don't remove the spring and plunger you could find it floating around in the bottom of the engine which could lead to destruction

[foleyit]

You will be fine without them (not that you have a choice with aftemarket cam). Like Ugly said its only function was for the decompressor. I've been running my hotcam now for over year and haven't had any problems. A fully charged battery helps too.

[Knips178]

the reason i ask is my brothers won't start and i don't think it has this piece in it. i wonder if that is why it won't start. It goes womp, womp, womp, bam, womp womp womp bam
if that describes it accurately?
We double checked timing, it has compression, but it won't kick over. the battery is fully charged to

[UglyMotha™]

Originally posted by Knips178
the reason i ask is my brothers won't start and i don't think it has this piece in it. i wonder if that is why it won't start. It goes womp, womp, womp, bam, womp womp womp bam
if that describes it accurately?
We double checked timing, it has compression, but it won't kick over. the battery is fully charged to




sounds like it's outta time, that spring and plunger will do absolutly nothing to your starting

[Knips178]

hmm, I don't know what is then. I've already torn it down twice to double and triple check the timing.

[foleyit]

Originally posted by UglyMotha™
sounds like it's outta time, that spring and plunger will do absolutly nothing to your starting

Do you know if you are getting a spark?

If you are getting a spark, make sure your are at TDC on your timing when putting the cam in. Also make sure you are not 180 out.

[Knips178]

Yes, I checked the spark. I replaced the boot and plug. Plus the Bam in my description is the sound of it firing once every few crank rotations.

The way i understand it, rotate the crank to TDC, when you see the T and make sure the cam is lined up with the two marks parallel with the top of the head and the third mark aimed up. Install the tensioner and make sure the timing is still spot on.

any of this wrong?

[foleyit]

You sound like you have everything lined up correctly.

May want to make take off the top cover again and check your cam marks alignment again with TDC.

Also, if you put in an aftermarket CDI and it is cold outside that could have some impact on your quad not starting. Throw your stock back on and see if that helps.

[Knips178]

it's stock cdi and now it about 60 degrees around here so it's not cold anymore. I don't know what it is????? It is getting gas. It is getting spark. It has compression. so the only logical thing would be timing so I guess once again I'll rip it apart and check, but I just don't think that is what it is.

[joeroadking]

First if you are sure everything is lined up correctly then check the keyway on the the crank sometimes the key gets broken gets broken and bike fires at the wrong time , happened to me

[Knips178]

to check that you would have to pull the fly wheel right?

[red400ryder]

mine is doing the same as your brothers...i got a new bore valve job new piston and rings and adjusted my valves and checked timing thousands of times and i know its right and i am also missing my plunger and spring..and a guy on here named 440ex told me this could be my problem so i am goin to go buy a new plunger and spring before i go off the deep end..hopefully thats the problem..i would try the same with his..later madmike

I just finished building my 440ex with a staage 2 cam. I left the spring and plunger out as per the instructions and my bike runs great. You can live without it just fine.

[MIKE400EX]

Is it me or does it look like the front & rear head bolt holes are welded up?:huh

[UglyMotha™]

Originally posted by red400ryder
mine is doing the same as your brothers...i got a new bore valve job new piston and rings and adjusted my valves and checked timing thousands of times and i know its right and i am also missing my plunger and spring..and a guy on here named 440ex told me this could be my problem so i am goin to go buy a new plunger and spring before i go off the deep end..hopefully thats the problem..i would try the same with his..later madmike





why waste your time and your money :huh do you seriously think that is your problem, what do you think the spring and plunger triggers a little guy to run down inside your cylinder and light a match :confused: that spring and plunger does absolutlly nothing to even come close to affecting your bikes starting, the only thing is dose is make it easier on the starter to turn the motor over and if your running an aftermarket cam i would definantly suggest that you not put it back in unless you wanna gernade the motor

[joeroadking]

Originally posted by Knips178
to check that you would have to pull the fly wheel right?
yes you will need a puller, unless it is so loose it is spinning free on there.

[Knips178]

well we're tearing the top end off today and replacing the rings, then double checking everything while putting it back together. so hopefully we'll get lucky or find what it is. If i figure it out, i'll post it.

[shamisc]

Maybe the timing chain jumped timing on the crank ??:confused: It deff sounds like a timing issue! Let us know!

[UglyMotha™]

Originally posted by Knips178
well we're tearing the top end off today and replacing the rings, then double checking everything while putting it back together. so hopefully we'll get lucky or find what it is. If i figure it out, i'll post it.



don't forget to hone the cylinder

[y2k400ex]

What cam is your brother running that it wont start????

If your running a Stock or XR400 cam it will not start with out the little spring and plunger. If its not in there the decomperssor stays on all the time. A freind of mine did this when he rebuilt his 400. It would try to start then back fire out the exhuast like it was out of time. He thought it was out of time untill i looked at it.

[Hondaluva]

Is it me or does it look like the front & rear head bolt holes are welded up?


I'm with you MIKE400EX what the he11 is going on with the two head bolt holes?

[y2k400ex]

looks like there a plug in there or something because you can see a shadow :confused:

[Knips178]

yeah, the jackass that packaged it left the guides in the head and shipped it in a small box with little packaging. The result is the head's bolt passages that you see smashed. Luckily, I pulled them out with pliers and the holes look fine.

[sheekiller]

sounds like cam timing pull valve cover and make sure when engine is true tdc meaning comp stroke the cam lobes are facing down because the sprocket will go no either way good luck

[M@MRACING]

i had the exact same problem with mine. i would bet that he doesnt have the spring and the plunger in it. if he is runing the stock cam it will not start.

[M@MRACING]

i had the exact same problem with mine. i would bet that he doesnt have the spring and the plunger in it. if he is runing the stock cam it will not start.

[red400ryder]

Originally posted by UglyMotha™
sounds like it's outta time, that spring and plunger will do absolutly nothing to your starting
I would just like to say...umm yes it does if your running a stock cam..cause i put mine back in like i said i would do before goin off the deep end and my bike is now running....so i guess you were wrong

[Knips178]

I took the whole thing over to Total Performance and had them look at it. They ripped the top end off and rebuilt it, now it runs like a champ. We still don't know why it was not starting, other than the plunger and spring was gone. he also said there was a ton of carbon buildup and the cam chain was stretched. So i guess i don't have any diffinitive answers on this one.

But, it now runs great so, I appreciate everyone's help