Hello There, Hope you're all fit and well

[bettyswolloks]

Hello there folks, hope you're all doing as well as you can this day.
My names Daz, I've been riding on the roads for over 40yrs here in the UK. And that's 40 proper years not 1 year repeated 40 times.
Anyway, the reason I'm here is to pick the collectives brain on tuning my XJR1300, Ive gathered most of the parts and all being well will spend this winter in the shed building my beast.
This is my plan.........
1380 pistons, Oversize valves and Kent YAM7 cams. All that lot is sat in the shed waiting to go in. When funds become available some flat slides will join the party.
Im currently waiting on a delivery from the states for the last piece of that little puzzle, the cylinder liners. Hopefully should be here in a month or so.

So yeah, that's Me and why I'm here, now I'm off to do some reading!

Cheers,
   Daz.

[bettyswolloks]

Ive also been offered a Nova racing gearbox kit, it lowers 1st 2nd and 3rd and raises 5th. The thing is it's for the FJ. As it's just a few gears and no new shafts I'm assuming it will fit my xjr gearbox. Anyone know if that's right or wrong?

[melloncollie]

Welcome, glad you're here.  Looking forward to a thread if you do one for your build, I don't see too many xjr's around here.

I believe the gears are the same, someone should be able to chime in with a definite answer.  Are the racing gears undercut?  Which flatslides are you going with?

[bettyswolloks]

I was thinking the 36s, I'm more interest in torque than bhp.

Ive just had a good read about there gearbox stuff, seems to be good stuff. A friend of mine has one for sale cheaper than that, and yes it's undercut Pal.

https://novaracing.co.uk/yamaha-fj1200-close-ratio-conversion-kit

They do a 6 speed close ratio conversion, but its silly money.

https://novaracing.co.uk/yamaha-fj1200-6-speed-close-ratio-gearbox

Im not sure whether or not I'll be splitting the crankcases yet. If I do I'll end up down the crank lightening rabbit hole, I think I'm deep enough already, for now LOL ;º)

[gdfj12]

Daz,

Keep in mind that if you want high torque, lightening the crank will tend to reduce torque and allow the engine to rev faster.

[melloncollie]

If you're doing anything with the gears I believe you'll be splitting the cases. 

That's interesting, I wasn't aware lightening the crank would have that effect.  Does it actually reduce the torque produced or does it only feel like it reduces torque?

Seems like a lot of people go with the FCR39's, I've never had a set.  I like my RS36's, though I'm basically stock.  The tuning and adjustments are mostly very accessible and easy to get to.  Its a tight fit and you'll likely make a mess but you can change the mains with the carbs on the bike yet, they're accessible through the drain hole in the bottom of the bowl.  Needle adjustments are super easy.  You will have to take the bowls off to get to the pilot jets.  And the pilot adjustment screws are a little difficult to get to, but manageable. 

I typed all that out and then realized you had the XJR and therefore a different frame; which might change how accessible or inaccessible some of those are.  Probably for the better if I had to guess.

[bettyswolloks]

Hiya lads, yeah I'm aware lightening the crank would ultimately affect torque. Not sure by how much though, can't imagine a way to even begin to try and calculate it!
But yeah lightening the crank would actually have a real impact on the torque, it wouldn't just be a placebo like say an ignition advancer is. If you see what I mean. Though I can't imagine it would have a massive impact., unless you lighten the flywheel and everything else along the way. It would rev a lot quicker as there's less mass to get moving/slowdown.

But a decision has been made. I'm NOT splitting the cases. That's a bridge too far at this stage of the thing. A close ratio gearbox would just annoy Me in the long run! So I'm just gunna stick to the top end overhaul for now, plus Its costing enough as it is without adding to the bill now. I'm really looking forward to getting started

[gdfj12]

Yeah, on most motorcycle engines the crank IS the flywheel, so any lightening would tend to decrease the torque some, but on a race engine that you need to rev up faster when you already have it making plenty of torque, lightening makes sense. As with all engine tuning and modifying, there are compromises involved with each modification. I wish you good luck your mods. Embrace the moditus, as many of us have. 

[Pat Conlon]

You will love the torque of the 1380cc engine. Remember with adding 15% more air you will be increasing your compression accordingly so be sure to add fuel to compensate both for the bump in compression and the added volume of air those 83mm pistons will gulp.
I am happy I ended up with the 83mm Ross pistons ( from Curt Andrews) on my current build vs. the 82mm Wisecos I had on my first build. Expensive lesson.

Follow Ross's assembly specs. and wash those cylinder sleeves with hot hot water and soap so your rings seat properly.

Cheers

Pat

[bettyswolloks]

Thanx everyone, I appreciate all your replies lads :ThumbsUp

Pat, do you have a build thread I could view? Any tips or tricks for Me? Found the Ross install guide, thanx for that.
Ive done this kind of thing before but it was all a whole other lifetime away.
My 1st build was a Kwak Z750, bored out to a whopping 810 LoLz That didn't last so well as on the 2nd test ride I got chased by the police and had to visit the redline a couple of times. That thing smoked like an old D10
My next venture was in the mad GSX-R1100 daze of old, can't really remember much about the specifics as there was a lot of recreational drug use back in the 1990s LOLz!! It had a big ape block and, I think, some 80mm pistons.

Anyway, I've got a Mate who has a dyno in his shop so it will be getting set up best I can on that thing. I dyno everything just so I know things are as good as they can be.

[Pat Conlon]

Sorry, no build thread on my engine. Randy @ RPM built my engine.
We have terrible fuel in Calif and Randy was concerned with running our pump gas with the higher compression ratio... so he shaved down the dome on the Ross pistons and added some volume to the squish area in the head....we thought a 10 to 10.5 to 1 compression ratio would be safe on a hot summer day in the desert with an air cooled 1380 beast running 91 Calif. piss water fuel. Randy used the stronger, lighter XJR rods on the Ross pistons. We also used an undercut 1st, 2nd and 3rd gear transmission cluster with a Barnett spring pressure plate running heavier 82lb green springs. A FJR clutch master cylinder makes the heavy clutch springs tolerable. We removed the skinny clutch plate from the back of the clutch pack so we now have 7 full sized fiber plates in the clutch pack. (See the clutch files for more info.)
I was looking for a street engine with strong low end torque and a good idle so I stayed with the oem cams and FJ BS36CV carbs. We have 130 mains, 45 pilots 130 air jets and special skinny adjustable needles raised all the way up. Sorry I can't remember the # on the Mikuni needles.
I'm running the stock ignition with a 5° advanced rotor (no vacuum advance) along with Dyna 3 ohm green coils powered from a dedicated battery circuit controlled via a spst relay. I'm getting a full 14.4 volts at the Dyna coils....really wakes them up.

We did do a rolling dyno just to check the fuel air ratio...but no power numbers so I am interested in your results.

Cheers.   Pat

[bettyswolloks]

Thanx for all that info Pat, cheers
I didn't even know such piss water existed, that's almost diesel LOL!! Here in the UK we have 95 and 99 at the pump. You can really the difference too. On I get around 130miles till I hit reserve, with 99 I'm into the 140s before reserve. Feels crisper on the throttle.
I've already gone through the clutch plates. I managed to get a sigma slipper clutch cheap, and I mean really cheap at £100! Brand new never fitted. It's a mad thing! I've only "used" it a couple of times, on the track of course. Left some pretty impressive dark lines on the exit of a couple of turns. We have a neat little track where you can run whatever you want around for 10mins for £15, it's handy for legally stretching the bikes legs.
I wasn't aware of the FJR option, you can use the Honda CB1000 master cylinder too.
So the standard conrods are up to the job then? That's good to hear, another reason to keep the crankcases together.
It'll be getting a pair of dyna coils at some point, along with the ignition module they do. They'll sit nicely alongside the M-Unit Blue, the Healtech Quickshifter and Traction control stuff I've already installed. A guy in Sweden has done a nice 1413 build, www.instagram.com/hashi_moto_motors/?img_index=1, talking with him he found it made the whole thing more sparky
I'll be running the standard carbs for a while, the flat slides are out of the financial equation at this point, I'm Skint for now till after Christmas!

It's a shame you didn't get any power figures, they would be good to know. Mine is doing 126bhp and a lovely 86lbft of torque, which is nice

[giantkiller]

My 1350 was built by Hank Scott. Used xjr rods also. Barnett plate stock cams. Pretty much the same as Pat's bigger motor. But still has wisco pistons. Hank's crank dyno. Put it at 167hp 114ftlbs. Hank was quite surprised. As he didn't think it was going to put out much more than the smaller 1280? Builds he had done before. But dyno numbers are not all the same on different machines.

[bettyswolloks]

The possibility of 114 lovely torks has me tingly all over
Good to know the XJR rods are seen with such high regard too.