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Discussion Starter · #1 ·
Hi guys, first and foremost, i'm a newbie to the forums, this will be my first post! I recently purchased a 03 foreman 450 4x4 es. it didn't run but was said to have a fairly recent (a year ago) rebuild. i can see fresh gaskets all over the engine which sort of supports the rebuild. anyway, here's my issue:

I live closer to 600 ft above sea level and have cleaned and recleaned and cleaned again the carb and put brand new Keihin jets in every spot, placed clip on the 3rd slot, as well as a new choke needle....this is a factory set carb. I have a new, clean Uni filter inside the box, and it has an hmf muffler.

When attempting to start and idle, it would lean puff and spit and die without always using a little bit of choke. swapped pilot up to a 52 and now, with choke, it will start and after warmed up, idle without the choke. however, with a stock 130 main jet it boggs at what I perceive as mid rev range. if I pull the air box lid off the rev goes higher but still not the limiter. If I pull the air filter off, it will hit the limiter. this to me says i'm way rich, but it's odd that i'm using stock keihin jets with hmf pipe and running rich. i've installed a 128 main and it's a little better still, but still will not hit the limiter with the filter on and for sure spits and sputters with the lid on the box.

i've checked valve clearances and are dead on. i've done a compression check and turned up 170 psi without loosening the exhaust valve, so compression seems good, and doesn't seem to leak down through the valves.
what am i missing?
without the air filter or lid on, i did a wot run through 4th gear and killed the engine. pulled the plug and cut the threads down, the porcelain is a very soft peach/tan color which i would say is probably perfect.

so why does my engine require less than factory fuel considering mods?

sorry for the long post but I like to be thorough. i'm definitely not a newbie to carb tuning, i rather enjoy it. but I just want to know if there is something I am missing as I am new to this particular machine

thank you all in advance
 

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welcome to the forums. put all stock jets back in, and set the pilot jet/mixture screw to factory settings, then go from there, with what and where you live ?, I highly doubt this will make that much difference ?. get the pilot jet/ mixture screw needle set to factory, then go from there.
 

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Discussion Starter · #3 ·
welcome to the forums. put all stock jets back in, and set the pilot jet/mixture screw to factory settings, then go from there, with what and where you live ?, I highly doubt this will make that much difference ?. get the pilot jet/ mixture screw needle set to factory, then go from there.
that is exactly what i did from the start. I completely disassembled the carb, soaked it in a bucket of chemtool, sprayed it clean. put it in the ultrasonic cleaner I have for 3 hours then sprayed clean. and repeated this process two more times. then i put in brand new, actual keihin brass and factory sized jets including factory needle and needle jet, and all new factory honda seals and orings. everything was dead factory. quad was lean at idle (but has an hmf exhaust and a brand new UNI filter) so i upped pilot to a 52 and adjusted the airfuel screw to a perfect idle. it idles smooth and starts easy. and spark plug is perfect color for idle.

a quick jab of the throttle and it responds perfect, does not bog or hesitate and returns to idle perfectly. the only issue i'm having is up top. it's feeding too much fuel to hit the limiter and it's a stock 130 main. if I use a 128 it's better but still will not hit the limiter without removing the air filter.
 

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welcome to the forums. put all stock jets back in, and set the pilot jet/mixture screw to factory settings, then go from there, with what and where you live ?, I highly doubt this will make that much difference ?. get the pilot jet/ mixture screw needle set to factory, then go from there.
that is exactly what i did from the start. I completely disassembled the carb, soaked it in a bucket of chemtool, sprayed it clean. put it in the ultrasonic cleaner I have for 3 hours then sprayed clean. and repeated this process two more times. then i put in brand new, actual keihin brass and factory sized jets including factory needle and needle jet, and all new factory honda seals and orings. everything was dead factory. quad was lean at idle (but has an hmf exhaust and a brand new UNI filter) so i upped pilot to a 52 and adjusted the airfuel screw to a perfect idle. it idles smooth and starts easy. and spark plug is perfect color for idle.

a quick jab of the throttle and it responds perfect, does not bog or hesitate and returns to idle perfectly. the only issue i'm having is up top. it's feeding too much fuel to hit the limiter and it's a stock 130 main. if I use a 128 it's better but still will not hit the limiter without removing the air filter.

Sounds to me like you need to go down 1 more main jet size if you are having issues due to the fact you remove the air filter.....
 

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Discussion Starter · #5 ·
welcome to the forums. put all stock jets back in, and set the pilot jet/mixture screw to factory settings, then go from there, with what and where you live ?, I highly doubt this will make that much difference ?. get the pilot jet/ mixture screw needle set to factory, then go from there.
that is exactly what i did from the start. I completely disassembled the carb, soaked it in a bucket of chemtool, sprayed it clean. put it in the ultrasonic cleaner I have for 3 hours then sprayed clean. and repeated this process two more times. then i put in brand new, actual keihin brass and factory sized jets including factory needle and needle jet, and all new factory honda seals and orings. everything was dead factory. quad was lean at idle (but has an hmf exhaust and a brand new UNI filter) so i upped pilot to a 52 and adjusted the airfuel screw to a perfect idle. it idles smooth and starts easy. and spark plug is perfect color for idle.

a quick jab of the throttle and it responds perfect, does not bog or hesitate and returns to idle perfectly. the only issue i'm having is up top. it's feeding too much fuel to hit the limiter and it's a stock 130 main. if I use a 128 it's better but still will not hit the limiter without removing the air filter.

Sounds to me like you need to go down 1 more main jet size if you are having issues due to the fact you remove the air filter.....
right, that's what i've been doing. i bought a 126 and 124 main. i'm just curious if anyone has any reasoning as to why i'm pulling fuel from the top end even though my air filter breathes better than factory and my exhaust flows better than factory.
most of the posts i've read, guys are using like 140-145 mains with similar mods and i'm at 128 and still going down? (still using keihin jets while tuning, i never use aftermarket, it's too confusing with having to use comparison charts lol)
 

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me thinks you need to tweak the pilot needle jet screw ?, or your carb is not clean ?.
 

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what bothers me the most ?, is the engine being over hauled ?..this worries me...lol.
 

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me thinks you need to tweak the pilot needle jet screw ?, or your carb is not clean ?.

He said he clean it extensively...... You think an incorrect screw position would make that issue happen????
 

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Discussion Starter · #9 ·
me thinks you need to tweak the pilot needle jet screw ?, or your carb is not clean ?.
carb is definitely clean after everything i've done with it. ive cleaned it more times than i typically ever clean a carb and with chemtool, an ultrasonic cleaner AND a blow gun, and multiple times.
will a larger pilot affect top end that much? especially since ive read on the forums here that a lot of people go to a 50/52 pilot for easier starting and smoother idle. i know each circuit of the carb will have a small amount of bleed over but i didn't think the pilot would affect the top end to this extent? and especially since my plug shows perfect color and jetting for idle mixture. i've never seen it be this extreme in all my years of carb jetting.
 

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Discussion Starter · #10 ·
what bothers me the most ?, is the engine being over hauled ?..this worries me...lol.
this is my only questionable thought. the guy said it was rebuilt within the year and the gaskets are definitely newer. he also gave me all the receipts and paperwork from the rebuild including parts and labor from a honda shop. so, i am pretty confident in it. however, i have not checked the timing chain and marks to verify timing but it runs TOO good to be out.
I also wondered about the cam lobes, if maybe they're worn out and not allowing the valves to fully open causing low air intake thus requiring less fuel?

food for thought
 

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what bothers me the most ?, is the engine being over hauled ?..this worries me...lol.
this is my only questionable thought. the guy said it was rebuilt within the year and the gaskets are definitely newer. he also gave me all the receipts and paperwork from the rebuild including parts and labor from a honda shop. so, i am pretty confident in it. however, i have not checked the timing chain and marks to verify timing but it runs TOO good to be out.
I also wondered about the cam lobes, if maybe they're worn out and not allowing the valves to fully open causing low air intake thus requiring less fuel?

food for thought
I agree, too many un-answered questions to be tossing questions at your carb and it's cleaning ?, I would start with checking the motor before I pulled all my hair out ? ( which does not leave me much hair as it is !..lmfao ).
 

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me thinks you need to tweak the pilot needle jet screw ?, or your carb is not clean ?.

He said he clean it extensively...... You think an incorrect screw position would make that issue happen????
yes, that screw/needle jet is what mixes the air to fuel ratio ?, if it's not set right ?, or clogged ? ( more than likely its clean ), it will not run right.
 

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Discussion Starter · #13 ·
me thinks you need to tweak the pilot needle jet screw ?, or your carb is not clean ?.

He said he clean it extensively...... You think an incorrect screw position would make that issue happen????
yes, that screw/needle jet is what mixes the air to fuel ratio ?, if it's not set right ?, or clogged ? ( more than likely its clean ), it will not run right.
well, i messed with it all last night and here's what I found. I went back to all stock carburetor. jetting, needle clip, EVERYTHING. It absolutely will not idle with the 45 pilot unless i use a little choke. Once i let off the choke, it idles for a second then begins to lean puff out the intake and die.
I paid real close attention to the mixture screw and it isn't changing anything. I put my 52 pilot back in and it idles pretty clean. but playing with the mixture screw, barely changes anything. i can turn it all the way in with little to no change and I can turn it all the way out with no change. something is up with the pilot circuit in the carb.
also, I noticed that the carb is flooding fuel on the airfilter side. is this normal for this bike?

i'm going to pull the front cover and check chain timing today, and may pull the cam and measure the lobe spec. Does anyone have a lift spec for factory camshaft?
 

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He said he clean it extensively...... You think an incorrect screw position would make that issue happen????
yes, that screw/needle jet is what mixes the air to fuel ratio ?, if it's not set right ?, or clogged ? ( more than likely its clean ), it will not run right.
well, i messed with it all last night and here's what I found. I went back to all stock carburetor. jetting, needle clip, EVERYTHING. It absolutely will not idle with the 45 pilot unless i use a little choke. Once i let off the choke, it idles for a second then begins to lean puff out the intake and die.
I paid real close attention to the mixture screw and it isn't changing anything. I put my 52 pilot back in and it idles pretty clean. but playing with the mixture screw, barely changes anything. i can turn it all the way in with little to no change and I can turn it all the way out with no change. something is up with the pilot circuit in the carb.
also, I noticed that the carb is flooding fuel on the airfilter side. is this normal for this bike?

i'm going to pull the front cover and check chain timing today, and may pull the cam and measure the lobe spec. Does anyone have a lift spec for factory camshaft?
something is up with the carb's passages, just like I said earlier ^^^^. just when you think the carb is clean ?..THINK AGAIN !..LOL. I have been down this road sooooooooooo many times ?!. to the naked eye ?, it looks clean ?, but what we don't see ?..IS WHAT'S INSIDE THE CARB !.
 

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Correct me IF I'm wrong, but I thought if u adjust the screw and there is NO difference the pilot is too large. Which doesn't seem right if he has to choke it....
 

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Correct me IF I'm wrong, but I thought if u adjust the screw and there is NO difference the pilot is too large. Which doesn't seem right if he has to choke it....
what your calling pilot, and screw is the same thing in my book. the pilot/needle jet/screw is what you adjust the air to fuel mixture. some folks call the idle jet the pilot jet ?, but I don't.
 

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Discussion Starter · #17 ·
Correct me IF I'm wrong, but I thought if u adjust the screw and there is NO difference the pilot is too large. Which doesn't seem right if he has to choke it....
what your calling pilot, and screw is the same thing in my book. the pilot/needle jet/screw is what you adjust the air to fuel mixture. some folks call the idle jet the pilot jet ?, but I don't.
sorry for the silence today guys, it's been a busy sunday but i have made some discoveries on this machine. First off, shadetree, you're correct. This has been my issue since the beginning. I used a 45 pilot jet and had the mixture screw at 2 5/8 turns out and it wouldn't run without the choke and no amount of adjusting it would allow it to run. so i bumped to a 50 pilot jet and again started at 2 5/8 on the screw. it would run but still had a lean puff every so often. so I went to the 52 and now it idles good. however, what I didn't realize previously is that the mixture screw really had very little affect. So, now I know that even with the mixture screw all the way in, it still runs exactly the same as all the way out? that one has me boggled.

On a positive note, today I removed the clutch cover, and to my surprise (thankfully) I found that the timing was off (advanced) by TWO teeth, so the valves were advanced by 2 teeth. THis explains a lot. The intake valve was beginning to open while the piston was still pushing UP on the exhaust stroke. The intake valve also CLOSED before a COMPLETE intake stroke thus why i was running rich at top end, it wasn't getting a full stroke of intake air lol.
so, I reset the timing and have a new cover gasket on the way. once it's all together again, i'll see how she runs and report back. But just so you all know, this 450 will run at least 2 teeth advanced lol.

SO, one more question for you guys (and let me preface this by saying, thank you for all of your help, it has been appreciated!)
Once the timing was all set, I set the tensioner and the slack was taken out of the chain. the "T" mark on the crank was dead on the notch, but the dimples on the cam were slightly before (to the right of ) the notch in the case. Is it normal to not be dead on with this machine? Do i possibly have a stretched chain?
There is no way to adjust the gear to get closer, as one more tooth over would now put the dots ahead of (to the left of) the notch in the case. I rolled the motor over several times and each time it lands the same way. I am an automechanic by day for a dealer and timing chains are MUCH MORE finicky about being dead on so that is why I ask. lol I've attached a pic of the dots for your visual verification!
Thanks again
 

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Correct me IF I'm wrong, but I thought if u adjust the screw and there is NO difference the pilot is too large. Which doesn't seem right if he has to choke it....
what your calling pilot, and screw is the same thing in my book. the pilot/needle jet/screw is what you adjust the air to fuel mixture. some folks call the idle jet the pilot jet ?, but I don't.
sorry for the silence today guys, it's been a busy sunday but i have made some discoveries on this machine. First off, shadetree, you're correct. This has been my issue since the beginning. I used a 45 pilot jet and had the mixture screw at 2 5/8 turns out and it wouldn't run without the choke and no amount of adjusting it would allow it to run. so i bumped to a 50 pilot jet and again started at 2 5/8 on the screw. it would run but still had a lean puff every so often. so I went to the 52 and now it idles good. however, what I didn't realize previously is that the mixture screw really had very little affect. So, now I know that even with the mixture screw all the way in, it still runs exactly the same as all the way out? that one has me boggled.

On a positive note, today I removed the clutch cover, and to my surprise (thankfully) I found that the timing was off (advanced) by TWO teeth, so the valves were advanced by 2 teeth. THis explains a lot. The intake valve was beginning to open while the piston was still pushing UP on the exhaust stroke. The intake valve also CLOSED before a COMPLETE intake stroke thus why i was running rich at top end, it wasn't getting a full stroke of intake air lol.
so, I reset the timing and have a new cover gasket on the way. once it's all together again, i'll see how she runs and report back. But just so you all know, this 450 will run at least 2 teeth advanced lol.

SO, one more question for you guys (and let me preface this by saying, thank you for all of your help, it has been appreciated!)
Once the timing was all set, I set the tensioner and the slack was taken out of the chain. the "T" mark on the crank was dead on the notch, but the dimples on the cam were slightly before (to the right of ) the notch in the case. Is it normal to not be dead on with this machine? Do i possibly have a stretched chain?
There is no way to adjust the gear to get closer, as one more tooth over would now put the dots ahead of (to the left of) the notch in the case. I rolled the motor over several times and each time it lands the same way. I am an automechanic by day for a dealer and timing chains are MUCH MORE finicky about being dead on so that is why I ask. lol I've attached a pic of the dots for your visual verification!
Thanks again
looks pretty close to the index on case and cam chain sprocket to me ?, is the T mark dead center on the sight hole ?, set it as close as you can without the piston moving, then check the cam chain sprocket index again, if may move dead on ?, but I can't tell you if your cam chain is stretched enough ?, your not showing the cam chain very well ?, but I always replace the cam chains when I tear into a motor, and even when I remove the front cover, that is the time to replace the cam chain while your in there !.
 

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Discussion Starter · #19 ·
yes, the "t" mark is center of the sight window. I didn't really tear it down. I left the clutches in and only retracted the tensioner. I was able to pull the cam sprocket off of the cam and move the gear around inside the chain two teeth, without removing it from the crank sprocket. then reinstalled the gear to the cam and tightened the bolts and put it all in time.
The dots are really close to the notch in the case but not dead on, but again, there's no real way to make them dead on. They're either before or after the way I see it
 

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yes, the "t" mark is center of the sight window. I didn't really tear it down. I left the clutches in and only retracted the tensioner. I was able to pull the cam sprocket off of the cam and move the gear around inside the chain two teeth, without removing it from the crank sprocket. then reinstalled the gear to the cam and tightened the bolts and put it all in time.
The dots are really close to the notch in the case but not dead on, but again, there's no real way to make them dead on. They're either before or after the way I see it
if you can't get the punch mark dead on with the case ?, then this tells me the cam chain is stretched a little, but not enough to make a big difference in the way the motor runs, least never has for me ?. I know I would put a new cam chain in, if it were mine ?..but it's not, your call :).
 
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