XJ750RL mods/build

If it's not related to a fuel issue you could route a piece of black or clear hose to a catch can mounted to the frame. This may give the smoke a chance to condense and also add to the overall look of the bike. You could leave the drain off the bottom for a bit cleaner look though. Just a thought.

 

+1.
You're not running an airbox, so you will get oil vapor out of the breather, and it will look like smoke (but isn't).

Put the airbox back on

 

The amount is what scared me. I didn't realise there wasthat much smoke/vapor that comes out. I was almost convinced it was piston rings but that was I think a knee jerk reaction. Is it normal for more vapor the warmer/hotter it gets?

 

I was looking to put in new ignition coils however the length of the new coils don't align like the originals. I noticed both mounting ends of the coils have a metal surface. Do both sides need to be bolted to the chasis for grounding purposes? And further does it havr to be both holes?

Further, the wiring associated with the coils is R/W & O for cylinders 1 and 4. R/W & Gy for cylinders 2 and 3.

The new coils have a positive and a negative terminal. Which wires would be to what terminal ? I worked out Gy and O to be positive and therefore R/W as negative. Is this correct?

Cheers gents.

 

Those are the wrong coils, they are the "shorty" coils as used on XJ550, XJ700's, etc. Both ends need to be supported, but neither is a "ground".

The Red/white wires are the +12V input to the coil primary side, and the orange and grey wires go to the TCI and are the "ground" for the primary side of the coils. The job of the TCI (among other things) is to create (open-and-close) a ground circuit for each coil at the proper time. When 12V is flowing thru the primary circuit of the coil (TCI has opened up the ground circuit for that coil), the current flowing thru primary windings of the coil creates a magnetic field, and this magnetic field energizes the secondary windings (the "spark plug side" of the coils). When the TCI closes the ground path for the PRIMARY side, current no longer flows thru the primary side, and that action instantaneously collapses the magnetic field that was being created by the current flow thru the primary side. This collapse of the magnetic field on the primary side triggers the release of the energy that was being built up in the secondary (plug wires) side of he coil, and thus a current is sent down the plug wires, thru the plug cap, and finally jumps the gap in the spark plug electrode, firing the air/fuel mixture.

 

Chacal, thanks for explaining that! That helps my understanding a lot.

Re the coils, apart from the mounting situation, would they work with an XJ750?

 

Yes they will!

 

Very nice bike, what year Hyosung GT650R are the forks from?

 

2008.

 

New question! Whilst I was working out how to mount the new coils, I spotted these two pieces of metal in the heat sink in identical places. Either side of the motor between cylinders 2 and 3... what's the story???

 

Little rubber? blocks to stop the fins vibrating in resonance with the engine and possibly breaking off. Leave them there, there should be about 15ish of them in the fins. Your bike is coming on well, ride safe.

 

New coils have gone on. Of note, once I finally got the firing order right, it sounded incredibly responsive. Great rev/throttle synchronization. Literally as soon as a decelerated, the revs followed suit. I was stoked. I then put back on the fuel tank and now it's still all good, but just not as impressively responsive as I had just witnessed. Given it was just the fuel in the floats, do you think it was just running nicer on fumes?
Just so strange that it appeared to change for no apparent reason.

 

I measured my valve clearances today and the reaults are per attached. Two things I noticed that caused concern. A crack on one of the exhaust side cam mounta but the thread relates to the cover bolt. Further marks of the cam chain striking the underside of the cover. Alarm bells or meh?

 

Personally, I don't like the crack... they tend to grow. If I could find another shaft cap I'd replace. If I couldn't find one... fab a metal ring to brace around it and a small amount of JB weld or something better? It would have to fit snuggly to push the crack back together and be crazy degreased before applying.

Either way, I worry about a 1/4 or so of the circumference breaking away and heading down the engine.

Here's some: (Is it a 750?)
https://www.ebay.com/itm/1982-Yamah...eca-Maxim-1980-1981-1983-015-47-/282656472988

There are 650s but not the one w/ valve cover threads:
https://www.ebay.com/sch/i.html?_od...aft+cap.TRS0&_nkw=XJ650+camshaft+cap&_sacat=0

 

That cam cap needs to be replaced, it is a problem waiting to happen. Is that cap on the left or right side of the cam tunnel?

 

it was running lean and hot with the fuel from what was just in the bowls

 

Or removed, cleaned, and welded.

 

Left - next to exhaust cam of cylinder 2.

 

Okay, just to make sure..........this cap is on the CLUTCH HAND LEVER side of the bike, correct? And it's on the exhaust cam? We may have a good used one available, just want to make sure it is the proper one..........those "short" caps with the threaded boses are on both sides of the cam tunnel, but one side is an actual BEARING cap, while the other side is merely a "placeholder" cap to accept the valvecover bolt (the inside surface of this cap is rough cast, not machined, since it is not a bearing).

 

Correct - Clutch hand lever side, exhaust cam.