440ex & YZ450F Questions

[SmokinEX]

ok i know this has been beat to death, run over and pissed on. i just need a few more questions answered.

i started putting the 440 together tonight, its been apart for years. i can't find the big cylinder sleeve oring. what are the chances i can find one at a local hardware store? if not, would a small bead of high heat RTV suffice?

will any 450 carb fit on the 400? i just got a yz450f dirtbike and im having some minor carb issues. hotstart/jetting. i was thinking if i could get a yzf carb i could use the carb on my bike now and use it on the 400. has anyone done this or is there much modifications to make it work?

the yz450f runs hotter then hell. the head pipe gets glowing red hot like 30 seconds after its started in the morning. im trying to play around with the jetting. i went for an all day ride yesterday and man did it get hot. twice the bike overheated and the smoke that came off the motor was insane. you could hear the fluids bubbling and hissing. i've never experienced that before. when i got home i check the rad fluid and she was gone. i was reading up on this and i know these bikes run hot, but this was a bit much. the owner said there was a bunch of work done to the engine, he wasnt sure what tho besides oversized piston and cam work.
is there anything i can do to cool it down on long rides? and is the 440 going to run that hot as well?
i want to get some header wrap for the exhaust, to keep some heat off my leg if nothing else. would that help cool it down in anyway?

[ridehonda400ex]

The yz sounds a little lean!!!!

[dxcody]

You can probably get by with RTV BUTTTTTT i would not recomend this. You might as well do it right the first time. You may try taking your cylinder into a couple different shops to try to find an ORING for it.

With a 440 bore, you MUST a SPAL fan, and a larger oil cooler, or you will have overheating problems. You can find a 350 turbo oil cooler on ebay that will mount up and all you have to do is run your oil lines to it. Dont forget if you get a larger oil cooler, it will take more oil.

About the yz, if it is gettin that hot, STOP RIDING IT NOW.
^^^^^^^^^^^^^^
You WILL cook your topend. Check for exhast leaks first off. Exhaust leaks=lean=overheating=cooked topend=rebuild.

Could be valve guide seals going out. Could be improper jetting. If it has a slip on/ full exhaust and isnt jetted properly, you will cook your piston and motor.

You will just have to do a Process of elimination until you find the culprit.

Also check ALL your fluids. If its low on oil it can cause this, if your low or out of radiator fluids it can cause this, if your radiator is clogged it can also cause this. Clean everything really well, blow out your radiator, check and make sure your water pump isnt shot.

A way you can check your water pump is if it is full of fluid it is good, if not it leaks out of a little hole in the bottom of the right side underneath the water pump.

It shouldnt get as hot as you said unless you were going slow all day on that all day ride you were talking about.

Dirtbikes overheat really bad while trail riding, you have to open it up down a stretch every now and then to let your radiator absorb some air, and cool down your radiator.

Otherwise it is not cooling your fluid down once it gets in your radiator, and its just shooting that hot fluid right back in the motor.

There are many things you need to check. Not trying to be harsh and i know this isnt what you wanted to hear, but you shouldnt have rode it when you knew it was overhearting.

I just went through ALL of this about 2 weeks ago with my 400ex and i got told the same thing.

Just check everything pretty much.

~Cody~

[SmokinEX]

thanks for the info, i don't really want to use RTV, but when i ordered my 440 (6 years ago) it came with the 12:5:1 piston. i plan on ordering the 11:1 and a stage 2 hotcam. but i am putting the motor together now to make sure everything is going to work before i drop a ton of cash in it, since the bike was in pieces for years. once its running and i know everything is working, im installing the gt thunder head bolts, 11:1 piston and cam, so then i will swap out the RTV with the proper o ring.

i check all my fluids before/and on every ride. i change the oil every few days. i only had the yz for a week so im still cautious, and this was the first long ride i was on.
That was the only time it over heated and at the time we had to take a path that was really tight, lots of hills, water etc, so I was going slow and had no where to open it up. I stopped in the middle of the trail and let it cool down for 20 mins. Then when we got off the path I stopped again for 20 mins. After that it was fine.

it's definitely jetted wrong, the idle is erratic, sometimes its high other times it wants to stall. I took apart the carb and the bottom was full of a varnish like coating from stale gas. i ordered a jet kit.

but would being jetted wrong cause it overheat this much? im kind of worried there is an underlying problem somewhere the seller did not tell me about.

[Zakradu398]

It sounds like the carb just needs flushed real good. And if it was tight trails, I wouldn't worry much about the over heating. My 450 likes to overheat on warm days in the real tight stuff

[Zakradu398]

Also, your jets could be could be clogged

[dxcody]

Yes i mean if you give the old carb a great cleaning, and all the jets, then that may solve all your problems.

On dirtbikes it is really really tough to keep them from overheating on the trails.

I always thought that quads overheated bad on tight trails but jees, dirtbikes are terrible.

[HondaPohl]

RTV is not an O-ring!!!!!!!!

[SmokinEX]

Originally posted by HondaPohl
RTV is not an O-ring!!!!!!!!

ya i was thinking about it before in the garage, don't think im going to go that route, im gonna head to a few shops around and try to get a 3 1/2" o ring.
do you install the piston without a ring compressor? i was having a hard time with the oil ring earlier

she gets pretty red eh. i was waiting for a jet kit, but im gonna take it off tomorrow and clean everything out. i'll play with the jetting to see if i can get it running better.

the path was extremely tight, it's fairly new, looks like someone started choppin down trees with a chainsaw to make it. (someone bought the land of original trail and blocked it off) but.. my friend had a cr450f and he had no overheating issues.
i was told there was alot of aftermarket engine work done to it recently, so that might make ir run hotter.

http://i300.photobucket.com/albums/nn25/smokinex/IMG_0396.jpg
http://i300.photobucket.com/albums/nn25/smokinex/IMG_0395.jpg

[tri5ron]

Originally posted by SmokinEX

http://i300.photobucket.com/albums/nn25/smokinex/IMG_0396.jpg
http://i300.photobucket.com/albums/nn25/smokinex/IMG_0395.jpg
that looks to me, to be SERIOUSLY too lean. I'm amazed it hasn't seized up already.

[SmokinEX]

ya im not driving it anymore until i get the carb jetting right.

back to the ex, i got the piston in the sleeve, it seemed pretty tight at first, it's now a bit smoother but still tighter then most piston's i installed. i carefully watched the sleeve for any scratches and it's still clean, just wondering if thats normal with the 440.

the cam plunger spring was stretched, i have A spring the same size but is there anything special about the spring/tension etc.
it would be safer to order them from honda, its only a $2 spring, but it would prob take a month to come in my from lock deal (their service sucks ***)