450R carb 440ex. Can't find help

[lelandjf]

Hello gents and ladies, sorry to post a new thread about this, but I have found no help or anything even touching on this in other threads.

I am having a great deal of difficulty getting the 450R carb to work on my 440 with a hotcams stage 1 cam, exhaust, and open airbox. Mounting was fine which "is the hard part."

It will start right up with a little choke (haven't cut it since I won't put it all the way together until it runs right). The hotstart is plugged. Once it's running, it backfires/pops out of the carb.

I have tried a 38/48/55 pilot jet, 165/190 main, switching needle positions and fiddling with the airscrew. Just slightly holding the choke on helps, but then it idles way to high. I am GUESSING that it is running lean. I can't make it go away. Once I put the stock carb back on, it runs fine.

Other people have said that it relatively bolts on with the physical mods to the carb, but mine is mounted just won't run right. I have had all the other problems with jetting on other bikes/quads, but never this so I don't know where to start or where to go from here. I have also searched everywhere and haven't found anything about this popping while idling.

Everything I have tried has done little if anything. I think the 55 pilot might have helped, but I am pretty sure that is way too big.

[cals400ex]

make sure the carb is on both air boots tight and has no leaks. you will probably have to move the air box forward for it to fit perfectly. it will probably be a bit problematic when really cold but after it warms up it should run fine.

[lelandjf]

the engine side airboot is definately on. when i tighten it, i cant turn it. the airbox side is on, but i dont know if that could be the problem. the old carb would run if the airbox was off ( i know this isnt good, but i wantd to make sure the airbox wasnt the problem). i am thinking that there might be something mechanically wrong. something missing or something i did wrong.

[44oEX]

ok well if you know jetting is the problem, then play with that again. don't just asume you lean run it a little then check the plug. get the slow circuit ( idle ) to run good. ( air screw, pilot jet ) then check the jetting at half trottle, ( needle ) get that dialed in, then go to full and do the main jet. you can just jump around and change stuff you have to start from the bottom and work your way up.

Now for your jetting, you will probably need a 55-60 for your pilot, and atleast a 190 for the main. I did have to much trouble to jet mine. just keep at it.

http://www.exriders.com/vbb/showthread.php?s=&threadid=143853

[khen]

I sucked some sand into mine over the weekend a couple of times(UNI filter let it pass :confused: ) and it would only idle with the choke on as well... it acted just like your's when the choke was off. Turns out my pilot jet was plugged. Perhaps your primary idle circuit is plugged somewhere?

Also when you say you plugged the hotstart does that mean you left the little spring loaded slide valve in there and then put a cap over the top? If you didn't leave the valve and spring in there I suppose that might cause a similar problem.

[Colby@C&DRacing]

Originally posted by khen
I sucked some sand into mine over the weekend a couple of times(UNI filter let it pass :confused: ) and it would only idle with the choke on as well... it acted just like your's when the choke was off. Turns out my pilot jet was plugged. Perhaps your primary idle circuit is plugged somewhere?

Also when you say you plugged the hotstart does that mean you left the little spring loaded slide valve in there and then put a cap over the top? If you didn't leave the valve and spring in there I suppose that might cause a similar problem.

That was going to be my question did you leave the hot start plunger in there? it has to be in there in the closed postion or you will have problems.

[lelandjf]

I said I "plugged" the hot start hole. There is a threaded hole on the top motor side of the carb. I plugged that hole as I have seen in pics of other people doing the same mod. It was an empty hole with one or two small holes in the bottom. There was nothing in there when I received it so I didn't know there was supposed to be a "plunger". Would I have to order this from servicehonda? I am familiar with how the part look up system works, but don't know what I would need or exactly what you guys are talking about. This is making me feel a lot better. I was pretty sure that there was something physically wrong. I can handle buying parts, I just like knowing how to fix it.

[khen]

In looking at the parts manual on servicehonda it looks like this would be the part you need 16019-HP1-671 . It says it's the hotstart valve set and appears to have the cap and spring, but I can't see the plunger(valve) itself. Most likely it's included with the set, but you might have to call them to confirm this.

It's a little pricey at $15.. you might be able to just find some sort of a rubber plug that you can press down in there to prevent air from entering the circuit. You just have to make sure that it's a tight fit and is down far enough to cover the air inlet holes at the bottom.

[lelandjf]

thanks for the help, i am going to try to find a piece of rubber to stick down there or buy the piece. I never would have discovered that on my own. These forums work great. thanks again for helping.

[Colby@C&DRacing]

The plunger is included it that part # and that should fix you problem