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DLBeltran74

No start!!!!

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Ok folks! I need help!  I have a 2004 Honda foreman trx 450 fm. I have spark, I have gas and I have air but this sucker will not start. It feels like air is being pushed from the carb into the air box. But then again it kinda feels like it sucks in then pushes out. It turns over and sounds like it wants to start but doesn’t. Has anyone had issues like this before? I can not figure out what’s going on! Someone please help!

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20 hours ago, DLBeltran74 said:

Ok folks! I need help!  I have a 2004 Honda foreman trx 450 fm. I have spark, I have gas and I have air but this sucker will not start. It feels like air is being pushed from the carb into the air box. But then again it kinda feels like it sucks in then pushes out. It turns over and sounds like it wants to start but doesn’t. Has anyone had issues like this before? I can not figure out what’s going on! Someone please help!

answer: the timing is off, maybe from a jumped cam chain ?. or a bent valve ?, or not enough compression from worn rings ?.do this test first, take a can of starting fluid, give the carb a SHORT burst of it, if it fires off them ?, then its a fuel issue, if it does not ?, then this leads me to think its a timing issue ?, or bent valve ?, which leads to not enough compression to fire off.

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DLB your comment saying air is being pushed from the carb into the airbox to me leads to timing being off, valves are not working as they should.  Could be a cam chain that has jumped a notch or two.  That was my issue a few years ago on my 450, backpressure into the airbox.  Good luck....

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On 11/25/2021 at 6:13 PM, bcsman said:

DLB your comment saying air is being pushed from the carb into the airbox to me leads to timing being off, valves are not working as they should.  Could be a cam chain that has jumped a notch or two.  That was my issue a few years ago on my 450, backpressure into the airbox.  Good luck....

Ok, I just put a new top end on it with a new carb. I new went below the piston. It was suppose to have been a runner before the piston/ring damage. But I replace the damaged stuff and never knew I had to make sure the timing was correct. So would I have to pull the whole engine and tear it all the way down to check the timing?

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It can be checked with the engine in DLB. but you need the front cover and valve cover removed.  See pages 7-25-26 in the service manual for a good description.  Just remember the TDC mark in the inspection hole rotates twice for every cam rotation so make sure you are on the compression stroke.  The valves will have some play to them on compression, will be tight on exhaust.  When on compression with the TDC lined up in the inspection hole, the cam sprocket dot should be lined up at 12 o'clock with the index mark on the crankcase.  If everything lines up your cam timing is set correctly.  If you are good instead of checking the valves you can remove the plug and feel a puff of air come out on the compression stroke.  But I'm not that good...lol  Hope this helps.....

 

I'm sure there are members here that can explain it better but this worked for me....

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43 minutes ago, bcsman said:

It can be checked with the engine in DLB. but you need the front cover and valve cover removed.  See pages 7-25-26 in the service manual for a good description.  Just remember the TDC mark in the inspection hole rotates twice for every cam rotation so make sure you are on the compression stroke.  The valves will have some play to them on compression, will be tight on exhaust.  When on compression with the TDC lined up in the inspection hole, the cam sprocket dot should be lined up at 12 o'clock with the index mark on the crankcase.  If everything lines up your cam timing is set correctly.  If you are good instead of checking the valves you can remove the plug and feel a puff of air come out on the compression stroke.  But I'm not that good...lol  Hope this helps.....

 

I'm sure there are members here that can explain it better but this worked for me....

Ok, now I remember what I didn’t do. I know I didn’t take that plug out to verify it was at tdc when I adjusted the valves. If I didn’t do that, would that prevent the quad from starting? 

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2 minutes ago, DLBeltran74 said:

Ok, now I remember what I didn’t do. I know I didn’t take that plug out to verify it was at tdc when I adjusted the valves. If I didn’t do that, would that prevent the quad from starting? 

If you set the timing on the exhaust stroke doubt it would start.  Thats why I said it would be easier with the valve cover off.  But try checking for the puff on compression....

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7 minutes ago, bcsman said:

If you set the timing on the exhaust stroke doubt it would start.  Thats why I said it would be easier with the valve cover off.  But try checking for the puff on compression....

Will do, I’ll check it out tomorrow. So another question. What will the valves feel like it the mark is showing. I have to valves, one on intake side and one on exhaust side. If I can see the timing mark will both valves have play or tight? Or one tight and one loose?

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3 minutes ago, DLBeltran74 said:

Will do, I’ll check it out tomorrow. So another question. What will the valves feel like it the mark is showing. I have to valves, one on intake side and one on exhaust side. If I can see the timing mark will both valves have play or tight? Or one tight and one loose?

Believe both valves will have play on compression....

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