high compression/jetting question trx450r

[bbrad mulvey]

I just installed a 14:1 piston(450r), and had my head work done(minor porting and polishing, new valve grind). I have a HRC kit/cam, full Yosh tri oval system, K&N/Pro Design pro flow kit. I am having some issues getting the jetting dialed in. I had a 195 main jet before the head work and piston and that is how it ran the best. Now when I firstly got the quad started it would ONLY start if I had the throttle wide open and it would ONLY Idle at wide open throttle. I dropped the main jet down to a 185(stock HRC jet), and i am 1 3/4 turns out on the screw, and now it will run and it will go into the high rpms just fine but it will not idle period! So I went and picked up new pilot jets. Now the stock jet is a 48 so I got a 42 and a 55 jet. I havent tryed it yet but I just wanted to see if I was going in the right direction with that.

My elevation is about 2400ft.
What do you guys think?

Also turning the black idle speed screw doesnt do ANYTHING, I forgot to mention that:(

[Hammer trx450r]

You will want to get a 50 pilot

[bwamos]

If you're main jets are dropping that low... I'd reccomend pulling your head cover back off and making sure you're chain timing isn't off a notch or 2.

When it's off it will be runngin rich but act lean. Making you tear your hair out until you realize the timing was off.. lol. (speaking from personal experience.. lol) My 330 when I first installed it was off a notch (not sure how I did it.. not rocket science, lol) it was acting lean but plugs were black at a 119 main jet.. lol.

With it fixed I'm running a 142-145 at golden brown.

Another sign, if it's off on the late side it can be hard to turn over because the valves arent opening and closing at the right times.

[bbrad mulvey]

that was the first thing I did as checked the timing( pull out allen head on right side/clutch side of case, turn engine over manualy until the dot in the engine lines up with aroow on out side of case.Then line up the camshaft sproket dots with the camshaft marks making sure that the lobes on the camshaft are facing up). That is how I took it apart, and that is how I put it back together, and that is what the service honda book said. So I am pretty sure that can be ruled out. Now I put in the smaller pilot just now and I notice that if I put my hand over the airbox holes I can feel air pushing out the box. Is that right? I am going to go and swap out the small pilot and put in the bigger one now and see what it does...
thanks
brad

[bwamos]

Are you sure? On the 300ex at least the Lobes face down (shallowest point on the cam on all lifters) not up when the crank marker is lined up. If your rockers sit on top of the cam the lobes should be facing down (unless the 400ex is just weird).

A 400ex expert on here could verify this.

Sounds like your Cam is 180 degrees from where it should be. Especially if air is pushing out of the carb instead fo being sucked int. Your carb is now the exhaust and your pipe is your intake if your cam is 180deg off.

[EASTHILL]

when jetting your bike,try to give the motor what its asking for.
your on the right track providing there are no timming or electrical issues.
dont think a smaller main jet is the wrong way to go either.
the high comp piston you installed may be sucking fuel harder
than the stock and a smaller main is in order.
just start with the main and work down the circuits untill she pulls clean- bottom to top ;)

[bwamos]

Blowback into the carb is a BAD bad thing.. you will burn up your valves very quickly.

Just as a note.. it appears he's the same bore, just higher compression. This alone should not affect jetting, much, as he is using the same volume of air, but just compressing it more when the valves are closed.

He ported and polished his head allowing a bit more flow, and a cam adding a little more.

So in theory,, he should only be going up or down a few sizes from what he was running previously. Unless he's changed more mods than he's showing like going form stock bore to big bore or stroker.

[bbrad mulvey]

Correct bwamos! I just added a piston, that is all, and ported the head. Now as far as the blow through on the carb, I figiured out that was a loose spark plug, I tightened it down and now the ******* kick starts like a 14:1! whew, its tough! So I went up and down with the pilot and they BOTH worked better than the stock 48. right now I have the 55 pilot and 185 main, I am going to go mess with the clicks on the needle right now, should I go up or down clicks on the needle?
thanks

[bwamos]

LoL, yea a leak around the spark plug will cause all kinds of weird things to happen.. lol.

Clip down will make it richer. Clip up will make it leaner.

At 50% throttle if your bogging on acceleration go richer.
if your sputtering go leaner.

Needle is really the last thing you adjust though. Set idle, get 100% throttle right, then jack with the needle. ;) Otherwise your making more work.. because a different main will make you readjust your needle.

[Hammer trx450r]

ill say it again," 50 pilot"

[bbrad mulvey]

ok I here is the waY i will leave it for today, I will come back tomorrow and try at it again
185 main
55 pilot
4th click down on needle
1 3/4 turns out on mixture screw

this is the way it is running the best, it does not have any problems from 1/4 throttle to full. But it still will not idle on its own. I can push the throttle about 1/4 way and it will idle a little high but it wont die anymore. Also it still takes wide open throttle to start it up everytime/ I will let you guys play with the idea in your head

Hammer>> Do you really think that it would be that much differnce between the 48 and 55 pilot? If so I will give it a shot, but I dont see how just that much about 48 will make a diff, but I have been wrong before!~
thanks again
brad

[Hammer trx450r]

I have just about the same mods and i had to bump to a 50 to get it to idle. and i wouldn't go under a 190 main( depends on where u r from)

[bbrad mulvey]

Im about 2300-2500 ft. Im in Idaho. I am going to mess with the timing today. I just dont feel comfortable with the air blowing through the air abox at all. I am going to try retarding it.

[Hammer trx450r]

Originally posted by bbrad mulvey
Im about 2300-2500 ft. Im in Idaho. I am going to mess with the timing today. I just dont feel comfortable with the air blowing through the air abox at all. I am going to try retarding it.

Sorry dude i did not read that reply about the air blowing out of airbox;)

[bbrad mulvey]

ok another long day of battling the ******* and I gave up on the stock carb, so I opted to put the edelbrock on it. Well I am still working on getting it dialed in but it does hol a lower idle(just a little above stock) but the carb seems kinda sticky(throttle wise). man it sure is nice not having to rip apart the carb to adjust it! So I had the niebor come over and say it was getting too late for that noise and he was opting to call the cops, so my brother told him to go ahead if thats what makes him happy!
So tomorrow I will work on it more, hopefully get it!

I guess my main issue is that the throttle likes to just rev up on its own sometimes. Im not sure what that is, so anybody got ideas? I was thinking vacume leak but I checked every where!

[bbrad mulvey]

ok timing was of, I was 1 tooth off duh! and I also stuck the edelbrock on there and man!~that things rocks! But I need the right jetting for it it has a really bad lag in it when I go to give it throttle so I am going to order up a bunch of needles and jets for it and use that carb. But when the power of that thing came on it came on! so right now I am just tweeking with the stock carb rejetting it and getting that dailed in. But still it acts a little fun with it on, it has two different idle speeds. When I firstly kick it over its really low but after I run it it is a little bit higher? And also when I am coming off of full throttle it sputters pretty bad. So I am going to try the HRC needle 4th clip down, 50 pilot, and 180 main.
thanks guys
brad