Whats your thoughts?

[POWDERSLUTx2]

I gotta 2000 Phazer 500 mod sled for the kids and it ran amazing a few years ago. Didn't get rode last year ,but when I have the track off the ground the sled upshifts and runs amazing like before. As soon as I put the track on the ground it won't upshift really. It runs like a complete dog. Ive taken apart the primary cleaned and inspected it and everything looks good.
I was thinking the primary spring might be worn out????
Surprise surprise they are back ordered...
Any other ideas fellas?

 

[rknight111]

Try Dynamo Joe, maybe he has access to one, look for the iBackshift banner.

 

[firstdoo]

Clean the carb. Might have a bit of restriction in one of the jets. Those old bowls gum up bad from sitting around.

 

[Dazzler]

Possibly old fuel??

 

[SUMMIT TREE]

More details.
Idles but as soon as u try to move Just bogs? Fuel/ carb issue. Possibly belt deflection way out to lunch??

or it goes but can’t build much rpm, seems boggy, hammer down but just wont rev out? That could be clutching for sure. Also fuel/ carb issue. Any chance of restricted intake? Like mouse nests or something blocking air flow? ( just spit ballin here)

any who, I would definitely replace fuel first off. No bueno? Then carb work/ clean/ rebuild as required. Most likely clutching isn’t that whack if it used to work. I highly doubt primary spring is wore out enough to matter.

 

[Cableguy]

are u running it with belt off? could be a rusted up jackshaft bearing impeding the engine run up
but also could be seized up fly weight on primary

 

[retiredpop]

Clean the carb. Might have a bit of restriction in one of the jets. Those old bowls gum up bad from sitting around.

Ahh, bringing back memories! Definitely start with the carbs. Those old Mikuni butterfly carbs they used did not take kindly to having fuel sit in there especially for that length of time.
There are 3 small fuel passage holes just where the butterfly valves meet the carb body. These supplement fuel flow in the transition from idle to higher rpm. If they are plugged or the small chamber under the welch plugs is gummed up you get similar problems like what you have. Before you go to the trouble of removing welch plugs though clean pilots and main jets and nozzle (part 36) in diagram.

https://www.ronniesmailorder.com/oemparts/a/yam/5003bdb9f8700212fc84066a/carburetor

 

[papajake]

If they are mikuni carbs their a lot better then the piece of crap carbs that were on the earlier models

 

[POWDERSLUTx2]

I took the carbs apart and cleaned them they look good.
Airbox is clean and no restrictions.
If I lift the track off the ground it goes like a raped ape,clutcheswork perfect.I put it on the ground and will only get half the performance. Primary won't even fully open and secondary doesn't even react.

Ill get a vid later today and try and post it up

thanks

 

[retiredpop]

If they are mikuni carbs their a lot better then the piece of crap carbs that were on the earlier models

Unfortunately they are the same Mikuni carbs as the original Phazers. They used butterfly carbs instead of the slide valve ones.

 

[Couch]

Check cold start plug - they tend to stick a bit ....if not properly seated you will be like a dog chasing its tail ...

 

[team dirt]

Just worked on my neighbours 85 doing the exact same thing. Pulled the carbs and soaked them for a few hours in carb cleaner. Blew them out put them back on and sled rips now. If it ran good before it’s totaly just carbs.