Quantcast
Jump to content

2003 Honda 400ex

STHbongrips

By STHbongrips
in Honda ATV Forum

 Share

Recommended Posts

STHbongrips Newbie

STHbongrips

Posted
Posted (edited)

Ive got a few questions regarding the top end on the 400ex.

Ive had a few problems with this quad since I got it and Im giving it one last go and doing it right lol. First problem is it keeps blowing the head gasket on the left side. The first time we figured it was just worn out and we replaced it, put it back together and it happend again. my dad replaced the cylinder because it was starting to smoke. We replaced it with a used one but it looked like it was in great shape. We bought a new piston and rings and another gasket. Everything was put back together, all gaskets looks great. Piston and rings were new and we figured it was ready to go. Well I guess not, because she started smoking again and the head gasket blew once again! This time I think we have it pretty figured out haha.

It tooks us a couple trys but we figured it out....one one the head bolts on the left side was coming out even when torqued to specs. So we got a set of helicoils and are going to install those. We also got a complete gasket set and will be replacing them all. We took the newer cylinder off to check out the piston. When the head was taken off we had planned on getting it ported and polished because we thought thats why it was smoking since the cylinder was in great shape and the piston and rings were new. But after taking off the cylinder we realized it was more then that haha. The piston has to be replaced again and same with the rings. The cylinder is going to be bored out to a 40 over and getting a wiseco piston and ring set. The bolt that was pulling out will be fixed, all gaskets will be replaced the head will be ported and polished. Im hoping that we have it all right this time, but Id like some input from you guys! I have some pictures of the cylinder and piston, can anyone explain why it happend? All fluid levels were checked and they were fine!

Piston1.jpg

Piston2.jpg

Piston1.jpg.9cdef603827b5bcc3cf989d06fc8f802.jpg

Piston2.jpg.98a7f5c39135463a07d0465c7c000a59.jpg

Edited by STHbongrips
  • 2 weeks later...
CRAZYKIWI Collaborator

CRAZYKIWI

Posted
Posted
Did you.check side clearences? Also did you mic the bore and.piston. did you check your oil pump and pressure? Was that side the side that the head bolt pulled out of?

Sent from Samsung Galaxy S6 via 5G

Has it stopped leaking now??

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
 Share
Go to topic listing

  • Popular Now

  • Similar Forum Topics

    • Cj Winds
      2009 Honda Rancher TRX420FA with shifting problems
      By Cj Winds
      I have a 2009 Honda Rancher TRX420FA with shifting problems.
      Usually it shifts ok when cold but after couple minutes it will stop shifting with no codes.
      The 1st shift clutch oil pressure when in first gear is 74psi. The 2nd shift clutch oil pressure when in second gear is 74psi.
      The 1st shift clutch oil pressure when in neutral is zero. The problem is when the tranny is in neutral the 2nd shift clutch pressure starts around 10-15psi and builds to 20psi. Is this normal?
    • Mikey509
      First time quad owner looking for advice!
      By Mikey509
      Hi guys, I was given a 2000 Honda Recon fourtrax 250 (I think that's the full name lol). The previous owner had it sitting for a while before I got it. It sat for another few years in my ownership. I got it up and going on its first test drive today!! I was wondering where everyone buys their parts from?  Coming from the car community, we have sites like RockAuto and many more. Anything like that for quads? Also would like to be pointed in a direction, if possible, for plastics. I am missing a few and would like to have it complete. I appreciate any input!
    • ButchM
      2023 Hisun Axis 700 fuel problem
      By ButchM
      Hisun 700 EFI. Replaced TMAP sensor had broken off . Fuel pump pressure 41psi. The only way I can keep it running (and runs fine) is to close off fuel return line. 
    • dkgg5755
      2003 Kawasaki bayou 250 carb problem
      By dkgg5755
      This thing came with a cheap aftermarket carb on it the problem I'm having is it won't start with choke installed into carburetor it will start and get run without it installed then bogs out after about 2 min run time I've checked timing , compression, checked valves for proper clearance , also did a smoke test for air leaks found none. 
    • BillR94
      1998 Polaris Magnum 425 starts but dies right away.
      By BillR94
      I picked up this ATV that had no spark. The previous owner said he was driving it and it died and would not start. He discovered it had no spark. He replaced the CDI and the coil with no luck. He got tired of it and I bought it. I replaced the stater and now it has strong spark. Now, it starts for a second or two then dies. It will not stay running. I have checked the timing and it is spot on. The valves are adjusted correctly. I see no warn issues with the cam. I put the original CDI and coil back on it. Same problem exists. Compression is at 65 psi (has decompression mechanism),
      I took off the muffler in case the issue was clogged pipes. No change. I replaced the spark plug. No change. The carb was an aftermarket so I put a Niche carb on with no change. I bypassed the fuel pump and that did nothing to solve the problem. 
      I don't know if this is a carb issue or an ignition issue. I am looking around locally for an OEM carb to try out but not sure that will fix the problem. 
      Can anyone help me solve this problem. I am running out of ideas. 
      Thank you for your time
      Bill
       

COMMUNITY SECTIONS

ATV FORUMS

QUADCRAZY MEMBERSHIP

Be a part of best online community of ATV riders and join thousands of people who love ATVs! Share your ATV photos, videos, ATV rides, get help with your ATV and more. Not a member?

SIGN UP TODAY

ADVERTISE WITH US

FOLLOW US ON

  • Automotive Webmaster
×
×
  • Create New...