XJ750RL mods/build

Thought I'd chuck up some pictures of my bike seeming I'm getting a heap of help from you all.

The bike looked great when I first bought it but the modified fuel tank was poorly constructed and I've since had little things here and there.

Whilst I sort out the niggly stuff, I've been doing the usual bolt on mods. I'm currently trying to get a tank I like and will suit a new rear end that I'm putting together to give it a cafe racer finish with some old school rat rod vibe. I think gold flake paint will be used somewhere but will see. First couple of pics are from when I bought it and the ones in the garage are where it is now. I've got a 3D printer too so I'm mocking up taillight brackets to mount a fiberglass rear that I'm playing about with.

 

Here's the fiberglass rear I'll likely go ahead with. May have to do some minor mods to the frame to have it fit.

 

Nice tail

 

I test fitted a tank today. I'll have to modify the standard mounts on the frame to allow the tank to sit flush with the seat but I think it'll do the job nicely.

 

Nice forks!

 

They're from a Hyosung GT650R.

 

Is that a 650 tank on there? Looks like it fits pretty well!
Did have have to rejet for exhaust not intake combo? I like the look, but am nervous about the issues it would cause for me.

 

I actually don't know what the tank is. I just compared it to some google pics and the shape is a little different to the 650 tank. I'm actually having a hard time finding a petcock for it as it's 45mm centre to centre on the mount holes. I think I'm going to have to cut out it's mount and get a new adapter plate welded in.

Tuning wise, I couldn't really say mate, it was setup with that combo when I got it and further a workshop did a little carb work to get it running right and at that time I didn't know what they did. I'm about to try and find out though.

 

Might be a 650, but it sure isn't an xj. Maybe xs..., may not even be yammy.

Can you show is a pic of the tank from the top?

 

The XS650/750/800 tank has a curved bottom seam. The XS1100 tank has a mounting tab thaat extends past the rear of the tank. I think Honda, but I have no particular reason why.

 

I've owned a 77 xs650 and the tank was pretty much like that one. It was what they call a Standard, not a SPecial.

 

Here are some pics. I find often the underside are more helpful but It looks like there may have been some previous mounting changes as I found some welding excess near the crooked mount.

 

Standard XS650s have the fuel cap centered. This one should be a SPecial XS650 tank or even a bigger model, like a Special XS750 or XS850. Here is a pic of an 83 XS650 SPecial Heritage tank:



Just one fuel tap is also typical of later models (1979 and later).

 

Been absent but the bike has progressed. Ive mounted the tank, seat and 3d printed a mount for the caddy taillight and light internals. New exhaust went on this week and am now possibly seeing a glimmer of hope. Still playing with the carbs and will get them back together soon... I hope.

 

where are the rear shocks from?

 

They came with the bike. I'm 99% sure these are the ones though:
https://rover.ebay.com/rover/0/0/0?mpre=https://www.ebay.com.au/ulk/itm/131352187403

 

Gents, how much blowby is ok?
I got registration today and tookcthe bike for it'sfirst proper ride.
I have a small filter on motor blowby outlet and think I have a problem. I'll video it tomorrow but after riding tonight, each time I came to a set of traffic lights, my headlight was highlighting fumes. When I'd rev the bike, more would vent.

 

That sounds like the float needles might be letting fuel overflow into the crankcase. Sniff the gas and check the oil level.

 

To be honest I can't be sure smell wise. The oil did possibly smell fuel like but wasn't 100%.

Here's a link to the video on YouTube.

 

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.

 

Frap, I sent you a message.

 

Check your inbox I have the part, you can have it.

 

As discussed Bushy, here are the pics.

 

What? You can't just swap a cap - they are inline bored once dowelled to the head, it might work but at the very least you should test fit it without the cam, then with it using some plastigauge. I've done this on car heads by selecting the best fit and testing this way, but there's no guarantees.
I once skimmed a 1100 vw head for a local lad, asked him how it worked out. He said the caps were getting hot. He had just assumed they fitted anywhere, result - scrap head, really.
Wash it and weld it would be my suggestion.

 

This is true, and this is the correct procedure to follow.

 

I checked the valve clearances not long ago and 5 of the 8 are out of spec.

The new shims required in accordance with the Haynes book are only 1 shim size away from the current ones. I don't know if these shims currently in the bike are the out of factory shims, but would one shim size in difference be enough to make an audible tap/knock sound whilst idling?

 

post your numbers for shim and clearances some charts in haynes books are wrong

 

The valve clearances tighten up as the engine accumulates hours; so when the tap goes away, that's when you start to worry.

There is also a tapping noise that is associated with one of the cam caps allowing a bit more end play than Yamaha intended (though your RL should have been fitted with the revised cam cap). If the tap is coming from the right side of the cam cover, that's the issue. It can be ignored as the clearance isn't large enough to do anything other than make a bit of noise (per the Yamaha TSB).

The third source is from the alternator chain contacting the case and an oil jet when the alternator chain guide fails. That tap will be louder, a bit hollow sounding, and increase as you pull away, or allow the throttle to slam shut (unlike the cam tap, which quiets down as engine revs increase, and does not get louder than from rapdly shuting the throttle from an off-idle conditon).

If you can post a video we can help you identify the source of the noise. My inclination is to say that it's just the usual valve noise.

 

looks like you can swap 2 shims and buy 3 shims
E3 move to E1
I1 move to I2
your chart in your book is correct