sputtering/bogging out on initial take off.

Could we see pictures of plugs please?

Bike sounded OK in the video except the revs seemed to take a while to drop (couldn't hear any bogging though :? )

If the revs take a while to drop it could be indicative of an air leak/idle screw set too high, have you tried the brake cleaner/ether/wd40 spray test round all the carb joints & throttle shafts? Just spray a tiny amount directly at possible leak sites (wd40 straw is ideal to get at inner carbs) and if the engine note changes you found a leak

 

Okay. You replaced the fuel rail o rings. Which requires you to break the rack. Which would request a bench sync and running sync. That's the cause of your hanging idle, or a vacation leak. Or a combo of the two Check the valves adjust if needed. Then perform a bench sync then a running sync n then check for vac leaks. That's what id do.

 

hey everyone. thanks again for all the help trying to diagnose this issue. the problem seems to have gotten worse. the bike will preform well on the road basically 2000rpms and after. when slowing down and dropping below that is when the bike become sluggish. and if i dont raise the rpms above 2000 when i take off it will jerk and sputter but eventually pick up after i get the rpms up.


i ordered a the gaskets to do the valve shim swap. and after that plan to get someone to tune and sync or find a tool and tutorial to do it myself.

until then i would like to figure out why all of a sudden the bike is acting this way.

the last time the bike felt this way a change of spark plugs was all that was needed. and the bike preformed tip top again.

as for breaking the rack and having to re sync. if i did not adjust the mixture screws when replacing the fuel rail o ring. what would justify a re sync? i pulled it apart and put it back together only using the screws on the rack.

thanks everyone for all your comments. i'll have to shoot another video and show you the plugs after todays ride.

again. thanks.

 

so weird update. i took out all the plugs to look at them. put them back in after photographing and started the bike up and it started and ran like before but eventually started to even out. took it for a ride and it isnt acting up at the moment. i tested all the plug wires and they were producing spark. i dont see what would cause this "temporary" fix to happen.

as for the plugs. all are pretty white except the number 4 plug. yesterday they seemed nice, but maybe the dark garage threw me off. perhaps im just losing my mind.

can they be white from the small amount of additive i put in to combat the moisture i may have had?

looks like im running lean. anything i can adjust while i ride and wait to adjust the valves?





also saw some oil on the fins of the motor on the kickstand side.. is this coming from the head gasket? cant see any oil above this point, or on the right side.





i'm thinking of spraying it off with engine degreaser and monitering it and see if i can spot where its coming from. there is just enough there to see. when i go to wipe it off with my hand i dont get much up at all.

what do you all think?

going to spray later today. thanks again..

 

The plugs look very lean from the pics, although not too clear on this screen so they could just be Clean instead of Lean. (hmm, screen clean lean... :roll: poetry in motion) I think there must be an air leak somehow and I'd be wary of riding anywhere in this state as you can overheat the engine (head gasket leakage may be a sign of this starting to happen).

Also, You do need to re sync after splitting the rack (bench sync first then running sync on warm engine, and the valves NEED to be in spec before you can get a good running sync too) so that all needs done ASAP.

Sync refers to the screws on the throttle shafts that synchronise the movement of the butterflies, not the pilot mixture screws. Have you read church of clean/9 yards at all? It's long but VERY important & useful info there...

That said, looking at the plugs I would say probably lean, possibly due to air leak. Perhaps it would be worth checking/resetting the pilot screws to standard as well in case they were played with... I don't recall if you're running stock airbox and filter? stock pipes? If you put your bike details/mods into your signature it's easier for people to remember

As far as the running problem that improved with the plug check, have you checked that your plug caps are screwed tightly onto the leads? (sometimes need a bit cut off lead to get them to "bite" again) and also while the caps are off you need to check that the resistors are not loose & that the resistance is in spec (US models are 5k outer & 10k inner, caps only)

 

thanks a bunch. i'll be looking for more air leaks today. no leaks as of yet. everything is stock. i'll update my profile later when i have time. and i'll inspect those plug wires. thanks for the info regarding the resistance.

 

i sprayed and i sprayed and every time i thought it was picking up, the engine would just stay and hang at that rate. only had a little bit left in the can. so it looks like more carb cleaner for me to pick up today.

if everything is stock. and plugs are still above mixture screws. would one need to adjust the mixture screws? i dont see why they are capped off with tamper proof plugs anyway?

 

After 30 years or so, mixture screws, their springs and o-rings have gotten covered with mild corrosion and need to be cleaned to work properly. If they are still hidden under their caps, it is pretty hard to clean them thoroughly.

 

thanks for the clear answer. thanks again. looks like ill be popping them off.

 

got the valve gasket business and doughnuts. going to replace this weekend

 

As I see it, ... 1, 2, @ 3 are "Critically Lean".
The Bike loves it like this. It charms you to leave it on the Lean-side for that big pull out-of-the-hole.
That mixture is explosively hot. Generates big heat. Hot-Rod.

Air-cooled Aluminum can't handle that for too long.
Be careful.
Critical-lean, dialed-in or air-leak related, can be heartbreaking.
You can go from Show-Bike to Parts-Bike during a pleasant afternoon joy-ride.

I have my 750Max dialed-in "On the Lean-side".
I pretend the Oil Cooler added helps-out a great deal with the cooling.
I look for some brown stain on the Insulator.
I use Marvel Mystery Oil in the gas if I'm going to run long.

If you have a ColorTune Plug you can dial-in quick.
With the Pilot closed; run-it. Use fans for coolng.
Slowly open the Pilot Screw until the Cylinder begins firing without missing.
Check the ColorTune Plug. It might be Yellow or Blue.

If it's Blue, ... continue turning-out slowly until you arrive at where the Blue just fades-out rich.
When you arrive at that mix you become a full-fledged "Tweaker".

You'll probably even fabricate some-kind of "Tweaking Tool", ... so you can reach-in to twitch two or three, ... and not hardly move the
Pilot Screw > || < that much, ... and be all-like, ready for a Merit Badge and a good cigar.

 

thank you so much..

how well does the pretending thing work? maybe i'll give it a try?


im still very concerned about drilling those little plugs out. something just doesn't seem right about it. after i or someone convince myself to drill those puppies out i'll let you know how it goes and if im celebrating or not.


thank again.. so much help.

 

If you can find a 900 Oil Cooler, ... with the whole sha-bang, including Adapter, (PN 90401-20089-00 BOLT, UNION) a hollow, Hex-fitting which secures the Adapter to the Oil Filter Platform, ... it's an easy fit.



The Cooler really helps on all-day jaunts down the Interstate.
When I put the Bags on and hit-the-road, ... I bring a Plastic Bottle of Marvel Mystery Oil along.

The Marvel smoothes-out the Burn and provides Top Cylinder Lube.

 

thanks a lot. i'll be looking around. you are quite a lot of help. thanks again.

 

I'm kinda coming into this late in the game, but are you POSITIVE that the battery is charged? It sounds like the way my bike was running when I had the alternator go out. It just wouldn't run under 2000 rpms...

 

you know what.. i should really check that. it fires right up in the morning. but i'll have to put the multimeter on it.

thanks alot

checked the valves yesterday.. thanks fitz. your tutorial really helped

intake

.08 .15 .10 . 08


exhaust

.15 .15 .16 .15

looks like i'll be getting some shims.

 

well. found some shims im going to pick up tomorrow and tested the battery at idle and at 2200 rpms.. looks like its working.. road it after i fully trickle charges the battery and still shuddered at take off. after the riding for about 20 minutes the bike evened out a bit and was more responsive at take off.. i dont know what im getting into.

shims in tomorrow though.

thanks everyone for looking and helping.

 

i have a quick question. when im cleaning out the pilot jet and paths with in.

when i spray some gum out and air in i should get gum out/ air coming from two places.. the pilot air jet and and pilot outlet. or the by pass hole?

anyone have any insight on this?

 

My 81 xj650 'stumbled on tip-in' when I got it. I too tried everything I could think of in the fuel system dept. I changed the IC ignition box and guess what? It ran fine! never count those ignition boxes out!

 

Is it possible that you have an intake manifold leak like a cracked boot or bad seal to the head?

I had my carbs dialed in pretty good and experienced same "stutter" off idle and found I had a crack in the intake manifold rubber. I also discovered that a PO had removed the intake manifold gaskets in favor of some yellow goop.

As soon as I installed four hand-cut gaskets and fixed the crack with Super Black RTV and silicone tape, the problem disappeared.