My exhaust creation.

Well, thats as good as I can do with a bit of plate and hammer work.
Let's see what happens, when I put the skin back on and start it up.

 

Oh, just in case anyone was wondering about the collector box construction and why all the metal is painted yellow...
My old man, who passed away a long while back now, had a little 6" x 4" trailer and he made a galvanised cover for it and painted it yellow.
The trailer is gone, but I still have the steel from the cover, which weighed just as much as the trailer I reckon.
A lot of projects around my house have super thick galvanised sheet in them obviously.
Yes, I'm a steel hoarder.

and while I'm at it... I suck at welding until I've been doing it for an hour. Everything before that needs copious grinding haha.

 

Just took it for a test ride, everything seems freeflowing, sounds a bit different (maybe) but...
1-4K(ish) is the same but Midrange is gone pretty much and winding past it is like grinding your teeth, on chalk, while you scratch your nails over a chalkboard.
So...
It might be on track, strangely... I'll raise the needles a notch (as I dropped them a notch previously because of the fouling at highway speeds) and see where I'm at!

 

I hope that you're welding outdoors, or better yet with the proper respirator.
Spare lungs aren't cheap.

 

Galvanized = smelly, harder to weld (contamination), poisonous.

 

Your engine is stock from what I'm able to gather, therefore you must retain some backpressure control. The pulses people are referring to equal high pressure, and low pressure in between pulses. Exhaust is the symphony of the engine, you want to find the sweet spot in design, that allows consistent pressure thorough out the exhaust. It will pulse and you can't stop it, however u can control the pressure it produces. Any drop in exhaust back pressure will transfer to the cylinder, and inconsistent uneven back pressures will intake speed and volume.

If you had serious engine mods ex... High lift cams or stroker crank and rod combination, the same principles will apply, but on different scales vs. Stock.
Race engines run high volume at high rpm's. A stock engine runs varing volume at varying rpm (street riding)
Race engines can blow out stock exhaust from more volume exiting over stock.

The average volumetric efficiency of a gas engine is 70%. A perfectly tuned engine is 100%VE. Even todays motors are only achieving an 85% VE

When you mess with the cylinder/exhaust valve back pressure you severely detune the VE, effecting idle, intake vacuum, power, mpg, low/mid and or high range power bands rpm range.

So minimal back pressure must be maintained.

I commend your efforts, but without propper knowledge your just pushing a square stone uphill.

 

You noticed that haha.
I agree completely, except, I can't help but try to figure it out.

 

Lol.. Keep on welding and learning my friend. I'm more than happy to watch.

 

Success!
Reset the needles back to clip 3 and everything is back on track.
Thanks for the great info Len, definitely made all the difference.

 

A final note...
Bikes runs fantastic in winter.
But was unrideable in summer.
Way too much heat retention in those, last forever, headers.
So... I have just received and installed these from www.tranzac.com.au
Looks fancy, sounds fancy.
Oh well...

 

Very nice.
Cheers, 50gary

 

I hate to update this.
But... Turns out it is my shite tuning skills that caused me issues as the new exhaust had the same issue when the ambient temp was 35C plus.

I'm still trying to come to grips with these mikunis, seemed more defined with the 750 and Hitachi's, but that could be rose coloured glasses kicking in also.

Still I have a shiney new exhaust system and a custom backup when it's not shiney anymore.

Shotgun method didn't work out how I wanted.

 

You’re fooling yourself my friend. Your issues are nothing to do with your welding, but maybe something to do with your design. However, the answer is mixture, mixture, mixture. Start playing with needles, heights etc. I would suggest weaker, given your issue is appearing when hot.
Let us know eh?

 

Did a factory 2.5 turns out, needles at mid point.
Same same when it was over 35c ambient.

Then

Bought some new coils from eBay...

35c day and I 'think' it may be solved but I have gone into a state of not believing anything and with all the learning of anything of xjs over the last 10 years, being thrown out the window because of this big, fat, thorn in my side.

I don't want a 40c day but I would appreciate it just to make sure I have finally solved this lunacy.

Still... It's all a bit of fun right?
Hand me another beer.

 

39C day.
I sweated, the bike may have sprung an oil leak on the cam cover gasket but... Wait for it... No crazy misfiring and tacho flailing

So... Yeah.

I might put the manufactured exhaust on the other bike, one day, cause I'm not going to mess with this one for awhile.

I replaced the original coils with second hand xjr1300 coils years ago, guess one is failing under heat. In the bin now.

Also replaced all the plug tops and tci with new replacements, way back.

Was close to buying new coils from Len a couple of years ago but... Well enough said.

*sigh*

 

Most excellent fabrication! Just wondering if your bike runs leaner now? Have you checked your plugs for color?

 

I wish I could answer that honestly. Way too many alterations before and after to accurately say.
I've had a lot of trouble with this bike, before and after the exhaust.
All the issues with the exhaust and running have turned out not to be fully, or at all, associated with it... so yeah.

 

Update.
I started with a bitza and blamed lots of things for the issues.
I believe the manufactured pipes could have been tuned via the carbs eventually but because of the tci failing, because of the regulator failing, I was stuck in a loop of insanity.
*Sigh*
Bike runs great now, tuned to the transac system and hasn't missed a beat. Obviously new TCI and new regulator.

My fancy manufactured system is in my shed