Jump to content
JRB

98 450es - won't rev up

Recommended Posts

Hello, I just rebuilt my 98 450es, idles beautifully, quiet, and smooth. just before the teardown and still, it will not rev-up. something electrical has happened. b4 i go further. has anyone experienced an issue similar. engine will not rev up without backfire. I know the cam to crank are in line. any idea's ? 

Share this post


Link to post
Share on other sites
 

That could be a lot of things , something as simple as bad fuel comes to mind ( water in it ) , dirty carb or #18 in this pic has a crack or hole in it , if   it runs perfect till 1/2 throttle ,   then spits , sputters , pops and back fires like it is out of time , check that #18 diaphragm  

image.png

  • Like 2
  • Thanks 1

Share this post


Link to post
Share on other sites
 

try adding a tad bit of choke and see if it changes when you thumb the throttle. 

Share this post


Link to post
Share on other sites
 

Fishflies: one moment it will rev, not for long. then the next time I start it it will not rev. just sputters, pings, knocks. I tried to get that cover off the carb, but one screw won't turn. (of course) the carb looks new. the plug wire is buggered up from the PO cut and spliced a new end on it. beginning of the story. (1) quad has a wench cobbled in it, (that was drawing power of the battery) . So I unhooked it, in the process I sparked the starter relay. (2) went to do a compression test an discovered the plug wire loose (just sitting on the plug)  plug was in only finger tight. (3) then it started to run poorly and got worse till it won't rev up without sputtering, knocking. (4) rebuilt the top end, piston, cylinder, rings. also replaced the cam chain (Bad). cam tensioner (Bad). oil pump (Failing). chain guides, exhaust gaskets. motor starts and run great at an idle. Ideas  ????

  • Like 1

Share this post


Link to post
Share on other sites
 

Sounds like carb issues. Is there any writing on the right side of the carb? Wondering if it’s an aftermarket Chyna special if it looks new.

 

I had a 350 rancher that had a similar issue and after removing, cleaning, and rebuilding the carburetor, I still had the problem. Put a new factory  carburetor on it and it has run like a top ever since.

 

Take some vice grips and pinch the screw that is stripped on the top cover to get it started. I agree with fish that it sounds like a hole in your diaphragm

  • Like 3

Share this post


Link to post
Share on other sites
 

Sounds like you got  a lot going on at once -----   I  think I would focus on the carb first , might be that simple ,  get the frozen  screw out like jeep mentioned by using small vise grip pliers and grabbing the screw head and breaking it loose , then clean the carb out good , if there is any trash in the carb like dirt or water , then clean the tank and petcock also , check the diaphragm while your at it --- if that is all good   ,  I would check the compression ,      then the  timing marks , as you might be 180 degrees out of time , or a tooth off , seen them run in both instances , but run bad  -------  

  • Like 1

Share this post


Link to post
Share on other sites
 

Thanks i will go after the carb issue. this acts a little like a polaris i had , it had a reverse safety that limited the rpm's. reason i mention it is the meter has both reverse and neutral lights lit. es system doesn't work . YET. 

Share this post


Link to post
Share on other sites
 
6 minutes ago, JRB said:

Thanks i will go after the carb issue. this acts a little like a polaris i had , it had a reverse safety that limited the rpm's. reason i mention it is the meter has both reverse and neutral lights lit. es system doesn't work . YET. 

 

 

so do I have this right  , the reverse and neutral light are lit all the time ?    the engine starts up and will run with the reverse light on   and it doesn't shift at the moment using the ES system ? 

Share this post


Link to post
Share on other sites
 

Fishflies - Yes both lights are on. when i got it, only the reverse light was lit. I sent the meter to AKATV and he fixed it.  the neutral light was bad. Engine starts and runs fine. PO added a foot shift. i've had the bike for 3yrs. vary limited use because of the engine work needed. 

Share this post


Link to post
Share on other sites
 
9 minutes ago, JRB said:

Fishflies - Yes both lights are on. when i got it, only the reverse light was lit. I sent the meter to AKATV and he fixed it.  the neutral light was bad. Engine starts and runs fine. PO added a foot shift. i've had the bike for 3yrs. vary limited use because of the engine work needed. 

So what you think happened with the lights  , maybe  the PO did the foot shift swop out , but  didn't do the wiring harness , meter and controller swop ??   -----Do you know about the ES by-pass harness 

Share this post


Link to post
Share on other sites
 

idk about a by-pass. i can see someone tried to inspect the wire harness at the angle sensor. 

Share this post


Link to post
Share on other sites
 

angle sensor connector is held on by a zip tie. idk ware your going fish, what could the es system have to do with the rpm problem?

Share this post


Link to post
Share on other sites
 

Post picture of the foot shift—want to see the lever.

 

post pic of the carb. Compare it to the model listed in the service manual. Yes it sounds as if there’s a hole in the piston valve.

  • Like 1

Share this post


Link to post
Share on other sites
 

Here you go goober. I ordered a new oem carb.

20210907_151953.jpg

20210907_151930.jpg

  • Like 1
  • Thanks 1

Share this post


Link to post
Share on other sites
 

thanks

couldn't see the carb model number.


Yeah i see a homebuilt shift lever on the ‘emergency‘ shift shaft.

  • Like 1
  • Thanks 1

Share this post


Link to post
Share on other sites
 

If you say it's acting like a rev limiter, it's probably related to the reverse light being on.

 

I'm not familiar with the 450's, but the newer machines have limp mode and if the ECU (computer) can't tell what gear it's in or it's reading two gears at once, it will go into "limp mode"

  • Like 1

Share this post


Link to post
Share on other sites
 

jeepwm69 Thanks. This is something that just started. I've owned this bike for 3yrs now. The neutral light never worked until AKATV did his magic on the meter. as Fish and Wilson point to is a carb problem. makes sense to me. I'll know when the new carb gets here. ES system is one on my list to fix. 

  • Like 2

Share this post


Link to post
Share on other sites
 

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×
×
  • Create New...