Just an XJ trait or something else??

Hi everyone.....first time posting but i have tried a search for this issue and could not find one. When the rpms reach around 5000rmp the engine starts to "stutter" and seems to loose power until about 7000 give or take....now is this just a thing XJ's do or could it be something else? Its an 81 XJ650 Maxim. Another quick question is i just recently got into learning more about this bike and think there are a few different models in 81 for the XJ650 maxim.....are all of these fork assemblies the same or more model specific? Reason being my brother had a slight accident with it and bent the forks. Thanks in advance and any input would be wonderful!

 

I understand that the ignition box can have cold solder joints on the circuit board and should be examined. Never had a single problem on mine. I'm also unaware of more than one type of fork for the 650 Maxim H. BTW, have a set, new seals waiting for a home.

 

Something wrong there as any motor/trait should not be like that , since its mid range it could be jets/aircleaner ect anyways something to do with fuel or as robert mentions the tci..

More info , as what aircleaner/exaust , when started ect ect....

Iwould not have a clue on da forks...

 

Forks will interchange. Robert's mention of the TCI could very well be it. Mine did this and it started acting up around 4600 RPM and was smooth as silk below that. I resoldered many times but it never really worked so I just bought another off ebay and have been cruising since.
Could also be carbs with a little gum on the main jets. Half a can of seafoam in a full tank will answer that in about the time it takes to run that tank through the bike.

 

5-7K - most likely air filter.
Not likely that its mains - the hole in the mains are too huge ... unless your fuel has sand type grains in it, and you dont have the screen in the petcock it wouldn't have blocked more than the pilots or air screw passage - much much lower rpm.
CDI - My virago's ate their CDI and always did it at a lower rpm and I'd lose 1 cyl. In a twin its noticeable, in a 4 its less so. If you're losing it on more than 1 cyl - maybe time to see if its a mated cylinder pair, and if it does use the exact same electrical path - which it would I think. then maybe its CDI.
My bet is air filter, then carbs, and then electrics in that order, but trouble shoot it before splitting the thing. And yea air filter can be done first - cant hurt.
Cool.
Srinath.

 

Thanks for all the input....i really dont think it would be the carbs as i took them apart and cleaned the jets and parts maybe 2 years ago. As for the forks could i get some pics and how much are you asking??

 

Has this just recently happened?, have you changed air filters or exhaust? spark plugs? Aftermarket exhaust have enough packing?

I'm not trying to question your carb abilities, so don't take offense, but this sounds like a needle issue to me.
For all intents and purposes, the pilots control the low range -to around 3 or four grand. The mains control WOT. The needles are going to determine correct mixture in midrange where you are seeing the loss in performance.

If you can say for sure that nothing has changed, then you can probably leave the carbs out.

And, no, XJ's don't do that. The ones that I have owned and ridden, have always had a very smooth powerband (until I started screwing with performance stuff)

 

I'll have to get back to you on the forks, they are in storage (but accessible) but I'm terribly busy this weekend. I'll be getting back to you.

 

Needle issue might be in the right ballpark. The tubes that the needles extend into are called emulsion tubes ... (or, as we Old Schooler's refer to them: Nozzles). The Nozzles have between 16 - and - 24 fuel metering ports drilled in to them - [depending on model]. If the metering ports of the nozzles are fouled ... and, they are small enough to get fouled in a hurry if the bike sits-around for more than a week or so ... you are going to have to dive-in to the carbs and poke them out ... clean 'em up and get all your mid-range and acceleration back. They're pressed in there. You have to go-in through the top and bottom. Remove the MAIN jet and washer ... remove the top-end ... and, drive-out the Nozzle tubes thorough the top, and inspect them. The ports are drilled straight through the nozzle at 90-degrees increments. You can hold them up to light and see through the close-side set on through the other side. Clogs can be cleaned-out with a perfectly-fitting cleaning probe found on a standard set of cutting torch cleaning tips ... Any welding supply store has these indispensable tools for carb-cleaning for 4-5 bucks a set. Check the carb sync before pulling the set to go Nozzle-looking-at ... a carb or two way out-of-whack will cause some -- hunting-for-the-right-mixture -- setting, too.

 

The only changes made to the bike were new spark plugs.....nothing specail just ngk's from a dealer and im pretty sure this was a problem when my brother had this bike. He also let it sit for about 2 years before i got it with half a tank of gas in it. :cry: When i took the carbs apart the jets were plugged solid and the needles had a green tint on the tips so i soaked the tips and jets in solvant and used a small needle to clean out the jets. So looks like another tear down for the carbs eh? Any special tools needed to push the nozzles out? Or special way to get them out without causing damage? Kinda green when it comes to carbs as the ones on this XJ were the first ones ive ever "fiddled" with. Thanks guys!
And take as much time as you need Robert im in no big hurry!!!

 

The easiest way to drive-out the Nozzles ... (which you are going to find to be needing some serious attention -- due to your remark about the 'Green' tarnish and varnish) ... is to sojourn to your local, well-stocked, hardware store and buy a 2 or 2-1/2 inch "Cap Screw" with threads matching those on the Main Jet. You can screw the Cap Screw into the Nozzle until the Cap Screw 'seats' ... and then -- Tap on the end of the Cap Screw driving it out. (( some Nozzles are "slotted and keyed" so that their position inside the carb body cannot be misaligned --- other's are not keyed and do not require precision replacement )). You'll be able to use the Cap Screw as a tool for resetting the Nozzle back in position. Start the Nozzle back into the carb body -- after -- lubing BOTH the Nozzle's bore and the outside diameter of the Nozzle. Then, put the Cap Screw up inside the lower section of the bore ... screw it into the bottom of the Nozzle and PULL the Nozzle back down into place. In the case of slotted and keyed Nozzles ... the Cap Screw will allow you to ROTATE the Nozzle -- clockwise -- until you feel the slot align with the key. Then, -- with everything cleaned and lubed -- the Nozzle will be easily pulled-down into place. To "Set" the Nozzle ... use a soft plastic or wooden dowel to seat the Nozzle in place. Do NOT attempt to draw the Nozzle down, using the soft, brass threads of the Main Jet. The threads of the Main Jet will be stripped -- or, worse -- the Jet will break-off.

The TOOL you will need is a STANDARD set of "Welders Torch Tip Cleaning Tools" Sold as a set, with ALL the tiny wire cleaning ends that fit the smallest carb metering ports drilled on BOTH Mik's and Hi-tot's.

The Nozzle is solid brass. The Nozzle can be cleaned-up with brass polish. In severely dirty and clogged situations ... 1) Shine the outside diameter's contamination off using fine steel wool. 2) Pull the steel wool making a long "Thick string" of steel wool. 3) Thread the string of steel wool through the inside diameter of the Nozzle and twist it as you pull the string through the Inside Diameter of the Nozzle. It is imperative that the Inside Diameter of the Nozzle is cleaned-out of all tarnish, varnish and contamination.

Use the Welder's Tip Cleaning Tool to clean-out each of the line of metering ports. After cleaning the Nozzle ... hold it up to light -- examining the Inside Diameter of the Nozzle ++ End to end ++ ... and, examining each of the tiny metering ports by looking in to the ports on one
side and through the tiny ports on the other side.

Special note:
In view that you have found GREEN contamination within the carbs ... it is also imperative that you review the POST regarding Vacuum Slide Stiction and "Clean-Tune" the topside's of those carbs, too!

Fire for effect!

 

Great thanks for the helpful info RickCoMatic!!! You wouldnt also by chance have a stator cover laying around also Robert? Or anyone else for that matter? :lol:

 

I do believe I've a spare. Again, got to hit the storage bin and that won't happen until next week at the soonest. I'll let you know what I find.