Quantcast
Jump to content

  • Do you own an ATV? Join our Forum!

    As a member, you can post in our forums, upload your photos and videos, use and contribute to our downloads, create your own member page, add your ATV events, and even start your own ATV club to host your own club forum and gallery.  Registration is fast and you can even login with social network accounts to sync your profiles and content.

Jacob Blocker

Honda 300ex has smoke coming out of engine case

Recommended Posts

I have been trying to get my 300ex to start for sometime. a few days i got it to start over and over and then the next day it wont start. I do the value lash and keep the covers off. I was (prob exhaust) smoke coming out of the covers with for the valves. I also noticed that the crank position marker had smoke also coming out, but i just thought it was from the head and it being in the cold. The hole for the position marker also has air come out when it turns over, but it is very light of air flow.

Share this post


Link to post
Share on other sites


I'm  not  sure  what  your  smoke is ..  It  could  be  from  ring  blow by  if it is   smoke  from fuel  actually igniting even though the  motor  refuses to  start or  it  could  be water  vapor  if  there  is  a lot of  humidity  and  cold  air from the  crank  case  " breathing".  There  will  be  movement  in and out  of the  crankcase  as the  piston  moves  up  and down  in the  bore.  You  normally  don't  see  that  because  the  crankcase  breather is normally  connected  to  the  air box so  it is  "breathing "  clean  air and it  is  the  only way  the  air  has access  to the crank case. The  reason this  happens  is  because as the  piston  rises  to the  top of the  bore  for intake  or  exhaust it is  in effect  making the  airspace  inside  the  motor  greater, so  air   comes in to  fill that  space. When  the  piston  moves  down  in the   intake stroke  or  power  stroke , it effectively  makes the  air  space in the  crank  case  smaller,  compressing  the  air  in there which then  vents  out through the  breather  tube to  the  air  box. There  isn't  a  great  deal  of  air  exchanged  during  each  cycle ,  but if that  breather  was plugged, any ring blow by would  build  pressure in the  crank case  and   soon  blow the  seals in the  motor.  Under perfect  conditions  of  zero  blow by, you would  never  get crank case  pressure  build  up since  the  piston  moving  in the  bore  would  only  slightly raise and  lower  crank case  pressure  as the  volume  changed  up  and  down  with the  stroke.  Long  story   to  say that  light  air  flow  you  find is  perfectly  normal  and expected.  :D

 

Share this post


Link to post
Share on other sites
7 minutes ago, davefrombc said:

I'm  not  sure  what  your  smoke is ..  It  could  be  from  ring  blow by  if it is   smoke  from fuel  actually igniting even though the  motor  refuses to  start or  it  could  be water  vapor  if  there  is  a lot of  humidity  and  cold  air from the  crank  case  " breathing".  There  will  be  movement  in and out  of the  crankcase  as the  piston  moves  up  and down  in the  bore.  You  normally  don't  see  that  because  the  crankcase  breather is normally  connected  to  the  air box so  it is  "breathing "  clean  air and it  is  the  only way  the  air  has access  to the crank case. The  reason this  happens  is  because as the  piston  rises  to the  top of the  bore  for intake  or  exhaust it is  in effect  making the  airspace  inside  the  motor  greater, so  air   comes in to  fill that  space. When  the  piston  moves  down  in the   intake stroke  or  power  stroke , it effectively  makes the  air  space in the  crank  case  smaller,  compressing  the  air  in there which then  vents  out through the  breather  tube to  the  air  box. There  isn't  a  great  deal  of  air  exchanged  during  each  cycle ,  but if that  breather  was plugged, any ring blow by would  build  pressure in the  crank case  and   soon  blow the  seals in the  motor.  Under perfect  conditions  of  zero  blow by, you would  never  get crank case  pressure  build  up since  the  piston  moving  in the  bore  would  only  slightly raise and  lower  crank case  pressure  as the  volume  changed  up  and  down  with the  stroke.  Long  story   to  say that  light  air  flow  you  find is  perfectly  normal  and expected.  :D

 

I would rather not take the engine apart to find out, bu i might have to soon. The one time i was able to get the engine to run (it was cold) it had a good bit of white smoke and when i killed it it left a kinda lingering smoke at the tip of the pipe. I also find it strange how hard it is to start it, although it could just the the carb (i have cleaned it a few times).

Share this post


Link to post
Share on other sites


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.


  • Similar Topics

    • By Panupong Pradchaphet
      I have a 2018 Sportsman 450 HO and from time-to-time I hear what sounds like exhaust noise through the cowl near the gas tank.  Could it be an exhaust leak or am I hearing something vibrating?
    • By dave3dracing
      Hi, I'm a new member
      Just bought a used 08 350 raptor with about 5 hours on it ( very clean ). Started fine when we got it. Now after a few mods (bumper, skid plates, air filter) Now will not start unless you pull in the clutch. I've checked just about everything and also checked that there is no pinched wires. Anybody have any ideas?:bangheadc: Thanks, Dave
    • By payne
      Have an Bear Tracker 250. Dont have the manual or any literature to help with. Anyhow, starts with pull start in gear, and electric starter doesnt work. Also, neutral light doesnt come on. Where should I begin?? Need some direction on troubleshooting all this. Thanks a million.

    • By Steven Workman
      So I have a Honda Fourtrax 300 year 1988. The ignition doesn’t start it with no sound. The headlights won’t turn on. It has a brand new charged battery, fuses are good, oil is good, gas is good, reverse is rusted, it shifts good, won’t jumpstart but when you try it will turn over, it will start if you jump the solenoid give it gas and spray starter fluid on the breather but it won’t stay on long but will stay on for the little time it does by itself. I don’t know what’s wrong and I need help!
  • Similar Tagged Content

    • By Chris Chitwood
      Hi, I’m a 16 year old that is wanting to get more into vehicle and mechanic repair. My dad has an old ‘96 Timberwolf that he doesn’t remember running since I was born. I want to get it running again as a memory for him and to help us be able to hunt together, and of course so I can learn how engines work more than the little information I know now. I’ve pulled the carburetor and gas tank off of it, and the carburetor is getting cleaned by a friend. I can post photos of the condition it’s in later, I’m just curious where I should start in my journey to get it running again. The power switch is broken off of the handlebar, so I am looking into fixing it, along with the pull cord. I’m afraid the engine is seized up, and I’m curious to hear any input anyone has. Thank you all.
    • By Adrian Ciotinga
      The title pretty much explains it all. When using the starter I can hear it spinning but not engaging the engine. The wheels also do not engage with the wheels when the clutch is out. The motor has compression if that helps.
      I am new to engine work and repair and I bought this quad with the idea of fixing it up (not knowing the full extent of the damage). The previous owner said it ran but sat for a year (I don’t believe that for a second after opening it up) and had bought a few new plugs and a starter motor, none of which fixed the issue.
      Any help would be greatly appreciated!
      I have attached a few pics of what I think could be wrong.




    • By weblex
      Problem: The ATV starts and runs at idle perfectly. But as soon as I open the throttle, the engine starts to slow down until it stops. On the attached video you can hear the sound of how it works: see video below
      Prehistory: there is a Polaris Sportsman 500 1998, which for about 1.5 years stood in repair, including also replacing CDI with one taken from the same ATV. Finally, the vehicles were on wheels, traveled several kilometers and overheated - forgot to fill the antifreeze Came back home in small moves. The next trip started well, but after 10 km there was a feeling of a small drop in power (even as the vehicle got warm completely) but still drives. Next trip - the situation is repeated. The next test of ATV through time and a huge loss of power from the very beginning. The engine sneezes, does not want to go more than 5 mph.

      What has been done: the carburetor has been replaced with a new one (inexpensive, $ 40), a new spark plug, a new ignition coil, the engine head has been removed, the piston is in good condition, valves were corrected - but the problem was definitely not in them.

      Ignition control unit is suspected. Who faced similar? Please help in solving the problem.
      Thanks in advance.
       
       
    • By Ashton Crawford
      Hello everyone, i have 2000 Polaris Trail Blazer 300 I’ve been stumped on for weeks. I’m having a lot of issues starting the quad. I cleaned the carb spotless because I thought it was a carb issue and bought a new fuel line because it wasn’t getting fuel. The carb gets fuel perfectly fine now but it won’t start. The spark plug I a little worn out but it’s good enough for just one start. The only time it does “start” is when I spray starter fluid into the carb. But it never stays on. It’ll start for a bout a second then just die out immediately even if you’re giving it some throttle and the choke is on. I have no clue what I should do. If you need more information, have questions, or have any slight idea what the issue would be and how I could resolve it. Please reply ASAP. Thank you.
    • By Connor Tuftin
      I have a 1988 300 Honda FourTrax, All wheel drive.
      My brother and I were fixing up this quad. We put a brand new battery and fuses in and it was running fine until we put the quad into reverse. As soon as it was put into reverse all of the electrical cut out and power wasn't making it to the head unit anymore and both of the brand new fuses popped. We figured there might have been a short from the starter or solenoids, but they are all working properly. At this point we don't know where to start looking for where the short could be. I'm just wondering if anybody has had the same issue or knows of similar issues that could cause these electrical shorts?
  • Recently Browsing   0 members

    No registered users viewing this page.


×
×
  • Create New...