2007 Hond fore 500 4x4 es trouble after top end rebuild

[Ejwill]

I rebuilt the top end on my 2007 Honda Trx500fe. It ran fine right after the rebuilt. But now when I try to crank it it blows Bach through the carburetor. I held my hand over the opening for the intake air and it blew gas back on my hand. Can figure out what happened all of a sudden. It was cranking and was able to ride it running through all the gears. Now can get it to crank just blowing gas back to the air filter. Need help again. Starting to think I should have walked away from this one.

[Gwbarm]

That sounds like a timing issue, have you checked to see if its jumped time.

[Ejwill]

Sorry for my lack of knowledge, but how do I do that and what would  cause that?

[Gwbarm]

Roll the engine over to the timing mark on flywheel and then remove the cam gear inspection cover and make sure the timing mark there is in the correct position.

[Ejwill]

GW, pardon my ignorance, but where is the cam inspection cover. Thanks for your help.

[Gwbarm]

Havent really worked on a 500 but this is what i found, no timing chain inspection cover.

 

Don't have to mess with the top end on a 500.

Get it to TDC by taking out the sight plug on the right side on the rear engine cover

Stand it on it's butt and remove front engine cover (I found it easiest to remove fan to create space to work)

Remove clutches, and timing chain is right there.

 

Thats crazy! I would take out the sight plug get it to top dead center and stick something in the spark plug hole to make sure its at top dead center you can also check where the valves are at top dead center with their inspection caps off. 

[Ejwill]

Ok, I’ll try it your way to avoid all that with the clutches.Is there a way to correct it if it’s not tdc? Without taking the top end down again?

[Ejwill]

58 minutes ago, Ejwill said:

Ok, I’ll try it your way to avoid all that with the clutches.Is there a way to correct it if it’s not tdc? Without taking the top end down again?

I got it on tdc and I stuck an Allen wrench in the spark plug hole and from the outside of the housing it was about  1 7/16” to the piston. That’s from the outside of the shell to the top of the piston. I don’t know if it should be closer or not the valves were loose, I could wiggle them and pick it up and down.

[Gwbarm]

Turn the engine slightly, if the allen wrench goes down turn it the opposite way until its at its highest point and check the marks to make sure its at top deaad center if it is timing is correct if not the only way to fix it is get to the timing gear. With the valves loose thats a good sign it is in time.

[Ejwill]

GW, I did like you said and turned the fly wheel when the Allen wrench was at the top the t  was in the window. The under line may have been a hair below the marks on the window threads but the t itself was pretty much in line I say pretty much because it depends on how you look at it through the hole. I did it several times and when the Allen wrench was at the highest the t was in the inspection port. If that’s good enough what else could it be. I just don’t understand how it ran good for a while then just quit. Won’t even crank it acts like to me it 180 out when it should be pulling gas into the carburetor it’s blowing it out. But the tdc is in line or so close it’s hard to tell.

AI on a search said it could possibly be a crankcase sensor or a cam shaft sensor issue causing it to fire in the chamber and blow it back toward the air filter. I have no idea what to try next

 

[Gwbarm]

If the valves are loose when there and cam lobes pointing down timing is good. I was suspecting it might be thats why i didnt want you to tear the engine down to find out timing is good. Check for spark, also put your finger over the plug hole while turning over the engine and see if you feel anything weird, it should blow  on your finger.  

[Ejwill]

I did like you said, I’m getting some pressure coming out of the spark plug hole . I checked for spark and it had spark. I’m having to charge battery now I left the switch on and ran the battery down. Is there some way the spark plug could be firing at the wrong time. Just guessing. Thanks for your help.

[Gwbarm]

The spark timing is controlled to some degree by the CDI, but i wouldnt go there yet, i would look further into the sensors you mentioned earlier.

3 hours ago, Ejwill said:

getting some pressure coming out of the spark plug hole

Getting lots of pressure or just some pressure, might check the pressure on a gauge, you should be getting lots of pressure.

[Ejwill]

Ok, will try that.

[Ejwill]

I checked it it was 180, I guess that’s alright. Now what? If you give up that’s ok, because I’m about ready to. It been a real pain in the arse!!

[Gwbarm]

 Great compression! I dont give up! I will stick with you and hopefully we can figure it out. You need spark, gas, compression all at the right time to run. You have all of those so it should run if gas supply is good. Of course there are all these electronic dohickies that get in the way of the basics for safety regulations.

[Ejwill]

Yeah, the electric things are what bothers me. You get up into some money when all that goes bad. And I don’t think I have what you need to check all that crap. But I’ll stick with it until we get too expensive or run out of things to try. Thanks for hanging in there.

[Gwbarm]

You have a great machine there definately worth the effort. I will do a little reasearch and see what i can come up with, anything else you can relay as to what happened when it stopped running backfire, stumble, idling bad, engine racing.

[Ejwill]

He, don’t kill me or quit helping me but I’m pretty sure I screwed up . I may have set the piston with an f in the window instead of the t. I couldn’t see that well without getting on the floor and with oil on the fly wheel I think I screwed up. I got out of my chair and took a swab and cleaned the oil off the mark and it was a f mark it’s really hard to tell sitting in my chair and it’s hard to get back in it by myself. Can I tear it back down and remove the piston, be sure to have it on the t. And reattach the piston. I’m not sure about tearing the front of that motor off. I checked the valves with it definitely on the t the intake valve barely moved, but the exhaust valve was very loose. Sorry for making a dumb mistake.

[Gwbarm]

When you rebuilt the engine if you did not mess with the timing chain and sprocket you should still be in time unless it was off initially. You can just reset the valve clearances with the T in the window instead of the F. Not a big deal, but if you set the timing gear on the cam with the F in the window instead of the T you will need to go back in and fix that. On the 500 cam chain does not have to be removed to put in pistons and rings.