Honda ATV Forum banner

How to set and adjust valves ( any 4 stroke motor ) !

85K views 51 replies 30 participants last post by  bubbasouthern.30.06 
#1 · (Edited)
We seem to be seeing alot of members joining..or already here ?..and buying..getting thier hands on ?..lol..an atv..then they ask us..ok..i bought..begged..barrowed my buddies atv ?!..lol..and now i need to adjust the valves...because it's making a loud tapping noise !..ok..maybe even a slight ticking noise ?..lol. well..the main thing i'm seeing..is when eveyone get's done with thier valve adjusting..then they come back and say..'' hey..i adjusted my valves..and not only is it louder now '' ?..but it won't even start '' !. ok..well..this is simple folks..when you did your valve adjusting ?..and you thought you had your piston on top dead center ?..you more than likely had the piston on top dead center on the exhaust stroke !!.
and now your asking me..how do i know the difference ????..right ???..lol. simple..this is a golden rule i learned many..many moons ago !!..( and yes..if you searched alittle..this has been covered many times here ! )..when you think you have the piston on the compression stroke to set the valves ??..do this...turn the crank backwards..as your doing this..watch the intake valves...if they start to move any when you are turning the crank ?..then turn the crank back the other way...until you see the index on the flywheel line back up where you first had it..then set your valves. iffffffffff..for some reason when you start to turn the crank backwards from where you first started..and the intake valves never moves at all ??..then turn the crank back to where you first started on the index...then keep turning it all the way around..until that same index line ..lines back up inside the case and flywheel...now your piston is on TDC on the compression storke !. again..always...always turn the crank backwards from when you first start..if the intake valves start to move when you do this ?..then you had it right to begin with..just turn the crank back the other way..until your index is back on the line/marks..set your valves..button everything back up..all done !. ifffff they never move ?..then you go back to the index..keep turning..all the way around..index lines up..piston is on TDC..set the valves..button it up..all done !. added : seems I forgot how to tell you to turn the crank backwards ? ( sorry..i'm old..and thank you.. to a member here for pointing this out that I left this part out here ). if you have a pull starter rope ?, remove the pull starter rope cover, now you can use the 17mm center bolt with a 17mm ratchet and socket to turn the crank backwards :).
__________________
 
See less See more
  • Like
Reactions: Honey_Badger2
#3 ·
And get a feeler gage that is bent at the end to make setting the proper gap easier. Using a straight feeler gage on these engines is going to give you a bogus valve setting.

Rick
 
#4 ·
Just did my 05 Rancher 350. It was super easy to reach the valves and a my straight feeler gages fit easily. I wish my other toys' valves were so easy to reach. The TDC mark is a PITA to see on this machine. Honda couldn't have made it much harder to see if they'd tried.

Btw, a way to confirm that you're on TDC on the correct stroke is to wiggle the rocker arms with your fingers to confirm that they both have a little bit of play. They shouldn't be touching the valve stems at TDC, so there "should" be a tiny gap.
Another way is to remove the spark plug and stick a small rod or stick in to feel if the piston is at the top of it's stroke.
 
#13 ·
Working with students trying to figure out how to get a quad running. I have not gone once to a grammar website to get help. The mark will be on the work, effort, and what is learned about mechanics in the shop; not an essay explaining in perfect prose why it did not start nor run. lol Shadetree thanks for the help!
 
#14 ·
Working with students trying to figure out how to get a quad running. I have not gone once to a grammar website to get help. The mark will be on the work, effort, and what is learned about mechanics in the shop; not an essay explaining in perfect prose why it did not start nor run. lol Shadetree thanks for the help!
thank you good sir !. I tried my best to explain in detail on how to do valves ?..so what if I mis-spelled something ?..or did not type it all out word for word the right way ?, seems everyone that has posted on here ?..had no problem understanding it !..lol.
 
#15 · (Edited)
lol, well put and I will heed your advice shade although I may have someone who has done this before help me so I don't mess it up. At the risk of sounding stupid, Since it's only a low clicking right now, do you think I can use it to plow this winter without doing too much more damage? I obviously don't want to destroy anything. And when doing the valves is that the best time to replace the cam chain as well? I want to have this machine for a long time and am going to try to do the right things, I'm just a little broke until spring.
 
#16 ·
I would be more concerned about the cam chain than the valves !..lol. if the cam chain jumps a few teeth ?..you might wind up slapping your piston with a valve ?..lol.
 
#19 ·
new here not sure if this is how or where you post a question but i have a question about a 98 honda recon i have air blowing out of the carb and sucking in on the exaust can anyone help thanks....and also let me no if this is the right way to ask questions thanks
 
#20 ·
Start a new subject post & list what machine you have along with what the history is leading up to the problems you have...
 
#22 · (Edited)
Auto part Vehicle Engine Tire Suspension part


Here is the way to find TDC on TRX300fx

Use a flashlight to look inside the left hole to see a "T on its side" lined up with the index arrow inside the case while you rotate the starter reduction shaft counter clockwise (hole on the right with the driver handle in it) Access is accomplished by removing the plug covers with a large screwdriver. The starter reduction shaft needs a 25 Torx bit.

Ensure engine is on compression stroke and not exhaust stroke.
 
#23 ·
View attachment 55306

Here is the way to find TDC on TRX300fx

Use a flashlight to look inside the left hole to see a "T on its side" lined up with the index arrow inside the case while you rotate the starter reduction shaft counter clockwise (hole on the left with the driver handle in it) Access is accomplished by removing the plug covers with a large screwdriver. The starter reduction shaft needs a 25 Torx bit.
ummm..yeah you will get TDC alright, but..will it be on compression stroke ?, or exhaust stroke ?. must be on compression stroke..big difference !.
 
#24 ·
Another simple way is to remove the spark plug put your finger over the plug hole and bump the starter or turn the flywheel by socket until you feel air pushing on your finger, then using a long dowel rod or screw driver stick it in the plug hole and slowly turn the crank until the piston is at the top of the cylinder and the "-"by the T is aligned with the notch in the cover.
 
#27 ·
Helpful is good. I have mechanic fear especially on Honda valves. Our dealer here gets pretty good dough for valve adjustment and the service interval is pretty tight. As I have a Silverwing too, I would save a bundle if I had valve confidence. Thanks for the post, shadetree.
 
#30 ·
Helpful info here..
Will be trying this tomorrow thanks to the manual,google and shadetree cross my fingers...My last valve job was around 3 years ago done by Honda .
it's a 2013 C.T.E. FPA so i figure it's due.....

Q : Not doing this regular maintenance would it be that I'm burning oil....1263Km, 785 Miles had to add almost a quart of oil....
Oh ya ODO just turned 10,684Km 6639 Miles

Maybe time for a 680cc...haha
 
#32 ·
The FSM for my 2018 TRX500FM1 says do not rotate the crankshaft counter clockwise, it will activate the one way decompressor system and give an incorrect measurement, and that slack in the rocker arms is the indication that I am TDC on the right stroke. Is there any other way to confirm TDC?
 
#33 ·
2013 420FPA.
Still haven't done this and the bike sounder louder yet but since it's nice day tomorrow will try to attempt....
So i been googleling how to do this,the manual is ready on the laptop and i think i have most of the tools to do this..
But when i get to the compression stroke to i adjust both valve on the compression stroke or do i do one or the other on the exhaust stroke....
 
#34 ·
Always adjust all of the valves on single-cylinder motors with the motor at TDC on the compression stroke. Verify your work after the adjustments by rotating the motor in the normal direction of rotation for two complete revolutions watching the valves open and close and stop at TDC again (on compression stroke) to double-check your adjustments. Do not ever rotate the motor backwards... if you go past your mark continue on two more revolutions and try again to stop on the TDC mark.
 
#35 ·
So the compression stroke is the piston on top or is it sitting at bottom,that's were i get mixed up...and then leave it when it get to compression stoke with T Mark and i adjust both according to the manual gap specs..
 
#36 · (Edited)
at the top or a hair past,, a very small hair. timing mark should help, unless you got a stretched chain.. TDC means top dead center. thats where you want to be. 4 cycle engine are a bit different than two cycles, they both are adjusted at TDC, with a 4 you have to make sure that your in the firing cycle, instead of exhaust cycle.
 
#37 ·
ummm, two cycle engines, or i think you mean 2 strokes ?, they don't have valves to adjust :). only 4 stroke engines have valves, least as far as i know anyway ? :).
 
  • Like
Reactions: rustneversleeps
#39 ·
Now those were old school, hey retro, i got one for you.....lol did you know those old Detroits had a habit of turning backwards... Lol my uncle owns/runs a well drilling outfit, his main drill platform rig has a 12-V (silver = forced induction + turbos) that beast has 2 blowers , and 2 turbos, one things for sure they indeed have a very distinctive sound. A old school mechanic once told me if you owned a Detroit and parked it over night, if there was a few oli spots on the ground the next day ? Something was wrong .....haha! Most if not all. Have been around always a had a rpm lope , and had that emergency air damper shut off, i did see one run away one time, i have no idea how high the rpm got before the guy closed that air flap shut off......
 
  • Like
Reactions: retro
#45 ·
I'm trying to adjust the valves on my 2018 Rubicon. Turned out to be a nightmare. The Honda service manual says to remove the crankshaft end cover and turn the crankshaft "clockwise". All engines turn both clockwise and counterclockwise. CLOCKWISE FROM FRONT = COUNTERCLOCKWISE FROM REAR. You have to specify front or rear or it doesn't mean anything.
I know over 90% of engines turn clockwise from front, but I don't want to make an assumption. Looking at picture of a recoil starter, it seems that this is one of those very rare engines that turn counterclockwise from the front (?).
So I tried to adjust them by turning it clockwise from rear (counter-clockwise from front) watching valve position. I adjusted the intake when the exhaust valve was depressed, it was .002" loose. Then I try to adjust the exhaust with the intake depressed and the exhaust valve is tight, no slack at all. I loosened it up a half turn and it's still tight. It couldn't have been that tight, it ran perfectly when I rode it in the shop.
Reading further, it seems this engine has one of those automatic decompression devices like my 2020 P1K has, which makes it even more important to turn it the right direction.
Do I have to put the engine back together and start it to get the decompression reset or something? Anyone know for sure which rotation this engine turns?
 
#46 ·
You’re looking for the sequence when the Piston is at TDC ( mark on flywheel) just after intake valves close and before exhaust valve opens. This is the compression stroke and both valves will be at rest. set b

The piston will also be at TDC on the exhaust stroke—and you’ll see the timing mark again)—don’t set them here.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top