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.

MarkinAR

300 falling on its face

Recommended Posts

So here's one I haven't beat yet, could use some input. Honda 300FW was running fine when one day it started bogging at WOT. Figured dirty carb so I cleaned it and still the same. Cleaned again once more by soaking overnight in thinner and then compressed air. Back together tonight and still falling at WOT. Tried a known good plug...nothing makes sense here. The float bowl does seap a bit due to old gasket, could it draw vacuum enough to interrupt fuel? 

Share this post


Link to post
Share on other sites


Absolutely will draw air intake on the bowl with a bad bowl gasket.  What happens is you get a corrugation of fuel and air going up into the needle.  Its like a carbonated effect. 
I would shut the fuel off and run the engine dry. Unscrew the bowl drain screw on the bottom of the carburetor to get all the fuel out. Wipe down the edge of the bowl where it meets the carburetor and run a beed of silicone around the seem.   Let it dry good over night and reset everything back as it was and fire it up.  If it runs good then you need to put a new rubber gasket on the carb. 

Share this post


Link to post
Share on other sites

Was considering running a bit of silicone to test before I ordered a rebuild kit just for the bowl gasket. Thanks for confirming a hunch. The gasket is all there, it's just flat from years of use. Probably the original 98. 

Share this post


Link to post
Share on other sites

Think it may have been the bowl gasket. I drew a bead of ultra gray and let it dry. Put it together and it seems to be back to normal. I also made a pump block off out of thin steel. The diaphragm looked a but rough and we never need the manual pump so it's just blocked off now. I left the pump so I could reuse the original screws but it's just decorative. 

20200409_144535.jpg

Share this post


Link to post
Share on other sites

Very nice work! I love making shit work! Nothing better then taking some leftover stuff you have laying around and using it. 
👍🏻

Share this post


Link to post
Share on other sites


Same. Its actually left over metal from when I made a battery tray for the Kodiak we used to have. wife was busting my chops about scraps of wood and metal just last weekend! Here is what it looks like now with 28's and 420 Rancher shocks. 

20200408_185957.jpg

Share this post


Link to post
Share on other sites

Gobs of clearance but too much tire. It needs gear reduction to turn them in peanut butter. Just have to go slow and not burn the clutches out. 

Share this post


Link to post
Share on other sites

Well that wasn't it. Have tried moving fuel clip, cleaned carb and its spotless. Tried another CDI and regulator. It just acts like a rev limiter at 60%  and it did not do this before rings and valve stem seals. Stumped. 

Share this post


Link to post
Share on other sites


Hows the plug look? 
Timing spot on ? 
Valves adjusted good ? 
Throw an inline spark tester and see if spark is breaking down at 60% throttle.  

Share this post


Link to post
Share on other sites

Plug looks good. Guess I'm going to pop the rocker cover off and double check timing. Fire and TDC are like 1/4 from each other. Perhaps I have it timed to fire and not TDC. Runs like a champ otherwise.  

Share this post


Link to post
Share on other sites

Guess I've largely discounted timing bc it fired right up after rebuild and runs perfect otherwise. Maybe with increased RPM a slight mistime becomes a won't run situation. 

Share this post


Link to post
Share on other sites

It could be. I have seen instances where timing was set bit once tightened on the chain tensioner it throws it off.  
its a long shot but im just throwing things out there. 

Share this post


Link to post
Share on other sites


Well I'll be. Turns out I had it timed to F instead of T. Bumped it 2 teeth and it runs like a scalded dog. Amazing it ran so well 2 teeth off before. 

20200412_123138.jpg

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 MarkinAR
      Picked this beauty up for zero dollars this weekend. It has been passed around several of my son's friends and the last kid was just tired of tinkering with it.  Mostly complete 96 300FW. The pic is my boy robbing the swing arm and rear diff for his 300 for a big memorial weekend ride. Wiring is garbage at the battery, kick start doesnt work, no coil, smoked like cheech and chong when it ran last. I figure a couple hundred and a few hours and this will be ready to ride. Journey will be documented on Instagram at @martincyclellc if ya wanna follow along. 

    • By AKMichael
      Hello All,
      I have a 1999 Yamaha Big Bear 350 4x4 trying to get fixed up so my grandson can go out in the woods with me.
      We have owned it over 10 years.  It got harder to start, until it finally would not.  Replaced the carb.  Right afterwards, it started and ran nicely, but after turning it off, would not restart.  Tonight I used starting fluid and ran, then died.  Adjusted the idle up a little, used more starting fluid and ran great.  It idled about 15 minutes.  Turned it off, and restarted.  Ran it around the yard about 5 minutes.  Turned it off, and would not restart.
      Any ideas or suggestions would be greatly appreciated!
      Thank you. 
    • By Susan Makowski-DeGraw
      My quad runs,  it starts up runs for about 10 minutes and then it dies if you let it sit for 10 minutes it’ll start back up ride for another 10 minutes and then die again, trying to figure out why it keeps stalling
       
       
    • By JacobSlabach
      So this’ll be long I’ll give all the background first to see my issue skip to the ***
      Hey I picked up a pit bike and a foreman for 800 the pit bike was running but the foreman was locked up.  Sold the pit bike but when I took the top end off the piston I only found half a piston left.  So knowing the rest of the piston was down in the crankcase I knew it had to be pulled and gone thru completely.
      to pull the motor I went ahead and pulled the rear end off and unbolted the front diff to pull the drive shafts and pull the motor.  Now I have the motor torn down completely and have all the parts of the piston removed.  I know the rod and crankshaft is shot (heat discoloration and too much up and down play rod to crankshaft).  
       
      ***so I’m wondering while I have the motor apart what should I check for?  I know this motor died from heat as the oil in the head smelled like popcorn.  So what should I check to make sure I fix the issue (overheating I assume) and not just the symptoms (blown up motor lol).
      so put simply I don’t want to just rebuild the motor to have it overheat and repeat the process after 5mins of running
      Here’s some pics





    • By SirMaxwell
      Any luck with manuals?
       
      I need a carb in the owrst way and am have gone down a lot of rabbit holes (over 90 tabs and counting). Factory calls for a Mikuni BST34/1 (I think, but need to check manual). I don't care what or who makes the carb, just need a basic reliable carb. No Racing etc, just puttering. I currently only have the cable with the round slide attached.
      Don't care if its round if I know what other parts to get to  make it all function.
       
      Thanks for help, and listening, gonna go chase more rabbits I guess.
       
      Max
  • Recently Browsing   0 members

    No registered users viewing this page.


×
×
  • Create New...