Petcock Vacuum

Yep, it’s not so much the screw needs adjustment, it probably does but until you remove it you can’t properly clean the idle circuit there. If you take care you should be able to drill into the screw and try a screw extractor.

 

I was able to free it up last weekend with a Propane torch. And just did the adjustment myself. It will idle all day now, without any Choke. But still no power at high RPM. I'm almost positive my valve spring's are worn and their floating at high RPM.

 

It feels like it has no compression above like 4k. Has no trouble reving, just doesn't accelerate it's a really weird feeling.

 

Only problem I'm having now is finding a set of Valve springs. Guy's have like 1 or 2 for sale on eBay. But it's starting to look like I'm gonna have to buy a Head to get a whole set.

 

I would hold off on the head purchase, make certain the carbs are fully sorted.
This you will have to do yourself or send them to a trust worthy source like @hogfiddles
After that you need to verify the fuel level in the bowls with a wet set.
Next is a running sync, small adjustments can make a big difference.

The valve train in these XJ's is good for 10,000 RPM +, you won't see valve float until you're beyond that.

 

Are all 4 pipes hot at idle?

 

Yeah, it's fireing on all 4. It pass's the Ear test. Rev is very responsive and quick. And it doesn't hang at all since I tuned the Carbs. It sounds great. While riding, it has good power down low. But once above 4 or 5k power just disappears. The motor is not struggling though. It's reving normally, you just don't accelerate if that makes sense. It feels really weird.

 

check your jets location fuel and air.
are your emulsion tubes clogged.

sounds like the carbs need to be cleaned. cant count on him having done it correctly

 

All of the issue's at Idle have been sorted. And I have an even build up on all 4 plugs now, slightly dark but acceptable considering I've never tuned Carbs before lol. It will sit at idle all day.

 

But the drop in Power at Higher RPM has not changed at all. I read that your valve springs can get worn out, and it will Cause float at lower RPM then normal. I'm not positive this is my problem, but it's my main suspect at this point.

 

Forget your valve springs, listen to @Simmy..
Carbs

 

Is your clutch slipping?

 

put a number on "higher rpm" same in all gears?

 

Mine has well over 100K on it and I knew one with over 300K up, neither of them suffered from valve float.

 

The guy I bought this bike from roached the original Motor by downshifting to 1st on the highway I guess. Not sure how you do that, but that's what he said. The current engine is from a wrecked bike he bought as a parts bike. And he apparently has never had it running with this motor in it. I gave next to nothing for it though

Reasonable suggestion, but i don't think so. It's hard to explain, best description is it feels like it looses compression above 5k. The Rev sounds normal, but there's just nothing there.

From around 5K till I get out of it probably around 8 or 9K. And yes it starts at the same point in every Gear. It seriously feels like I loose all Compression above 5K, and it just stops pulling all together.

 

Im sure, but i think we can all agree that 2 of the exact same engine's can end up in very different condition 40 year's after they rolled out of the Factory.

 

I could definitely be Wrong about this, but after learning the symptom's of Valve float it has become my primary Suspect. It's just too close to ignore. But I have no issue putting it on the back burner to insure I've covered every possiblity.

 

Compression can't dissapear, valve float sounds horrible, like a million hammers banging away in the headunmistakable. You have an issue with your carbs - or the tci, forget valve fl

 

My point being, that age and normal wear and tear don't seem to affect Yammy valve springs much.
If the PO had over-revved it enough to damage the springs, all the valves would be quite well bent or trying for freedom out the top of the head.
What you might have is a few slightly bent valves, but if your compression is ok, it's not really likely.

 

Okay, that's a relief cause I didn't wanna pull the Head apart again. It's funny that you mentioned TCI because I lost Spark the night before last. The Bike came with a box of Parts that included a Stator. I installed it with no change. I ordered Coil's and they will be here on the 24th.