XJ 750 82 Weak , no power

Hello Everyone!
I took over my fathers xj750 1982 europemodel that had been sitting for at least 10 years.
Leaking fuel and everything so I started with tank , changed peacock and all hoses. Cleaned tank.
Ordered a carb kit from Taiwan, looked ok.
( only choice from Sweden)
Cleaned carbs with soaking, mechanical and ultrasonic. I will say I cant do more. CoC.
Set fuellevels wet in spec.
Comp test 110,120,120,120
Checked valves, some exhaust were tight, now in spec.
Coils in spec.
Timing seems to line up fine.
New spark plugs. ( several times)
New Shaftseals carbs. ( Hitachi)

Bike had #43 pilot jet and #120 main , the Taiwankit only had #43 and #122 , but its 4-1 system , stock filter so I guess its not totally wrong to step up.


Now to the issue:
Its starts really easy, cold as warm.
But as soon you touch the throttle it bogs down and dies if you try more.
If I use the ”choke” and plays with clutch I can get away but its weak and hesitates.

This tells me its starving for fuel, but sparkplugs are also really black(dry) . But it might be that I’ve mostly idled in garage..not really running it…
Ive used colourtune and it looks good.
Ive synched carb without ycis tool, but its not to far away.

Ive no more ideas, for me it feels like it at least would run ok.

Long text but important to tell whats done.

Help is needed…‍ before I melt it down…..

 

I wonder why you would replace jets? Clean them, put them back in. The numbering in the Taiwan kit may not be accurate and there is no need to replace a 120 with a 122 anyway, unless the book calls for a 122.

 

They had a lot of this green stuff from old fuel and was really hard to get ckean, one of them was ” corroded ” so when I saw the new ones it felt better . But I think I actually swapped them one time with the OEM ones but it was the same …
It feels like something else , could ” one size” really make this difference?
Just by putting a needle inside jet I can confirm that 122 (Taiwan) is slightly bigger than OEM 120.
So OEM doesnt feel drilled.

 

There are little tip cleaners that you can pick up for your carbs. I have found that even with sonic cleaning, it will never get the jets as clean as they need to be. Don't forget the small jet in the bowl, that one is sometimes hard to get clean. It needs to be clean to have the bike start and run the way it should.

B12 chem tool works really good for getting the green stuff off the parts. I don't know if you can get your hands on some there, but it really is great for brown and green junk in the carbs. Just make sure you keep it away from all the places that have rubber, the throttle body area that moves the flies is a place not to spray from inside or out.

https://www.amazon.com/Carburetor-C...hvlocphy=&hvtargid=pla-4583657826282753&psc=1

 

Thanks, this feels like a good idea..
I’ll try to get this !
In the end it might not be enough cleaned…

 

Are you allowing the engine to warm up before touching the throttle?

 

Yes I have , after a while it idles fine without ”choke” , but it behaves like that anyway…
I will try to find B12 as Timbox suggested, looks tough to find in Europe but lets see.
This green stuff is really hard to clean, so if I have that inside any channels somewhere, specially in the bowl, that might be a reason….

 

Those compression numbers seem low, don’t they?

 

I don't want to sound trite.
Bogging down is definitely something that would happen when the air filter is blocked.
Obviously it would happen for a whole lot of reasons also if the bike isn't stock.
I've raised the needles too high and had issues like bogging down on the freeway. So yeah. Fuel/air...

 

I had crazy bogging over half throttle one time - turns out a main jet had come adrift and was suitting in the bowl. So its getting rich too soon.
Like cds1984 suggests you can drop the needle to check on an improvement then down jet further it needed. needles also wear => rich.

 

I checked again , 139 , 142, 140,143
I mixed numbers with my outboard…

 

Air filter is new , even tried without.
How do I adjust the needles? Doesnt seem to have any ”steps” on needle. Put shims to lift?

 

I checked my jets so many times. It feels ok.
Im not sure about needle adjustment, for me it feels set and non adjustable.

 

I plan to put carbs in ultrasonic again, bought a mech cleankit so I will make a surgery on these 4 bastards. (Again)
After that I think I need new parts for carbs, im not 100% comfortable with the taiwankit I bought.
Also find new main jets # 120 as it was before. Old ones looked really bad ,so new is needed.
I let you guys know how this steps works out.

 

Sorry.
I have mikunis they have adjustable needles on the 900.
750 has the Hitachi which is not made to be adjustable.
Hmmm.

If the bike is basically stock... I don't want to add to the ever increasing insanity that your search for perfection may be becoming... But. Bogging down can also be caused by timing advancement.
Cringe, yes the electrical system.
TCI, reluctor, regulator.
Normally this would never be an issue of course.
But I'm just mentioning it.

Needless to say if you had a spare TCI lying around it would help dispell this avenue of doubt. Argh.

 

Break the rack and remove throttle shaft seals, remove mixture screws, springs, tiny washers and tiny o-rings before using ultrasonic.

 

Yes I Will do this!!