1981 XJ650 maxim intake boots YICS

Measurement from float bowls is off from fins to block gasket.. carb 1 is 2-1/8th carb 4 is 1-7/8th. picture showing how i did it

 

To all thats following this post i got it sorted ..after ordering the wrong boots they came in the mail yesterday ....on my 650 # 3 and 4 were wrong they were tilted down, what i did was use #1 and 2 of the new ones i got stuck them on 3 and 4 ... all things straightened out with vac ports up top.

 

There is a reason why we recommend buying most parts from @chacal.
He almost never sends the wrong part, and when he does he fixes the problem quickly.

 

Paid $22 bucks for these wrong boots only used two of them/gaskets/clamps ...lets see how they hold up to the gas additives.... got two spare if anyone needs em

 

looks like i made a big mistake getting these boots. now have vacuum leak right where it bolts to the head..... got to get the 1980 model year intake boots

 

Last chance lol... going to make thicker gaskets and use RTV ..seems like a lot of 650 owners recommend RTV ..could pull there carbs off blindfolded not had em off so many times...

 

got some fel-pro gasket today it was 31 thou thick before compressed... on 1 and 2 the rubber ring was as hard as the outside, straight edge showed it was not level... used flat tile and 500 wet/dry grit paper got that sorted.... did the same with the other two (china junk) boots the rubber ring was not above the boot flange not level surface ... did not use RTV... Passed the garage test with spraying carb cleaner.... have yet to road test

 

Still got the surge after 6k ...using sea foam now ... used propane no vac leaks, spark plugs not rich or lean......runs perfect at idle hot/choke cold, runs perfect at 65mph... surge 6k and up, it will pull through surge to red line. notice it at steady 70/75 mph... giving it full throttle and backing it off ...making sea foam do its job (i hope) have to do a longer run and do a plug chop


The carbs on these bikes have three circuits - three paths by which fuel/air can make it to the engine. There is the enrichment (a.k.a. "choke") circuit, the pilot circuit, and the main circuit.
Enrichment circuit - manually controlled by the "choke" lever. This circuit is used to enrichen (add more fuel) to the mixture to make starting and running a cold engine easier.
Pilot circuit - This the primary source for low-RPM fuel/air supply.
Main circuit - This kicks in at higher RPMs.

So if the pilot circuit is clogged or otherwise not working correctly, then that can be masked by the enrichment circuit providing the extra fuel that the pilot circuit is *supposed* to be providing.

There is also an adjustment on the pilot circuit to adjust the fuel/air mixture (rich/lean). If the pilot adjustment was severely lean, then that would be just like having clogged pilot jets.

 

This is just a thought. By surge do you mean rpms go up but speed dose not increase. If it is doing this it might be a slipping clutch.

 

No rpms do not go up clutch not slipping

 

I’m kind of with @lostboy - what exactly does surge mean? Drop in rpm like somebody shut off the fuel, or an increase in power/rpm like some invisible monkey was pulling on the throttle? Or something else?

 

Let me explain, got throttle at 7k rpm and up.. rpm does not drop at all, speed goes up giving more gas, this feeling is like fuel on fuel off .... fuel on fuel off...no back fire, something like when you have to turn the petcock to reserve running out of gas ... no loss of spark... thats a surge right, now i am going to give it full throttle, pulling through the surge .. then backing off throttle i see an increase in power around 6k when backed off, the problem is when it gets past half throttle thats when it starts, backing of to half throttle its ok.. so i wind it up again and do the same thing trying to get the sea foam to do its job.... could this be a partial blockage in the mixture screws small passages... gas tank is clean.. petcock filter clean.. brass in line filter clean... fuel flow good .. float bowl levels up to bowl gasket.... all jets clean and passaged blasted with carb cleaner.. no vacuum leaks, spark plugs light tan, clean stock air filter, intake boots to air box tight... no holes in carb rubber diaphragms....

 

I don't think the pilot circuit has that much influence anymore at 1/2 throttle or more - you would be on the main circuit - which mean emulsion tubes. And of course the emulsion tubes have like 12 teeny tiny holes instead of one teeny tiny hole.

So is it almost as if you're running on 4 cyl, then 3, then back to 4?

Could just one of the carbs be starving for fuel? Like a sticky float valve or something? I'd be interested to hear the opinion of somebody who really knows their stuff like @hogfiddles if this sound like a carb issue.

Other thing that comes to mind for me is an intermittent ignition issue.

 

Yeah i made sure them tiny holes were clear in the emulsion tubes twice...no its not dropping a cylinder i dont feel that.... its like i am towing something and the thing i am towing puts the brake on for a split second.... yes starving for fuel, got to be that? but if it was it would not pull through it right......like i said the engine will pull through that spot until the speedo is bouncing off the limit peg, if it was an ignition issue what could that be, i dont feel a dead cylinder or miss fire... coil ohms ok... whats going on with the Main circuit - This kicks in at higher RPMs. thanks for the input.... i guess if the sea foam dont work what next, been trough the carbs three times, going over everything...

 

starving for fuel in the higher rpms makes sense.. like the bowls can not fill fast enough, gas cap vent is ok...has anyone drained the carbs and re filled with sea foam then crank over to start, let soak over night then drain bowls... or should i just go through two tank fulls with the sea foam additive see if that clears out problem

 

What air filter do you have?

 

Stock air filter.... but wait i found something ..i decided to check the fuel flow from the petcock using clear hose into small bottle flow was good..... then i checked the flow through the brass in line filter.... fuel flow slowed down a bit... wow could this be it.... checking the small brass filter the inlet and outlet is not more than an eighth of an inch...fuel line is 1/4 blowing through it its clear but the brass filter does have some restriction, its clean no blockage.... i read somewhere that fitting an in line filter along with the petcock filter has some restrictions,... i remember now, it was on the Honda 550 forum.... road test in the morning fingers crossed

 

The sintered brass filter should let enough fuel flow, a lot of us use them, unless yours is bad. Try removing it and replacing with a straight connector to test. The petcock filter, I don't think will restrict anything as it is a large screen designed to trap larger particles from passing.

 

Well after a run out without brass filter it was a lot better 60 mph 70 mph I could tell the difference winding it to full I felt a bit lag then surge backing off throttle it's ok.. now getting back on freeway up the ramp it felt like a spark problem stumble misfire when giving it full throttle stumble under load.. the spark plugs do look ok, but they have been sitting 21 years..

 

Brass filter with small orifice. NGK BP7ES plugs