TRX 2 - The tuned 850 one!

[coxylaad]

this bike shouldn't really be spending much time below 5000rpm i would have thought.

going to try and get it on the dyno this evening if possible.

[cobbadiggabuddyblooo]

The airbox resonation pulse is tuned to provide a neutral pressure in the box at overlap.
Meaning the pulse wave from the airbox will cancel out the the pulse wave from the exhaust pushing fuel back through the inlet valve during overlap. You'll find it will manifest itself around the 4000rpm mark with std cams.
You can loose anything upto 4-8hp at this point if things are out of tune with each other.
This will not really shift with the kent cams having only 2* more overlap than std.
Kent cam inlet open 5* earlier but exhaust close 3* earlier than standard on overlap hence only the 2* gain in overlap.
You can see the table on page 40 of my rebuild thread.
Std trx has 24* overlap and I have 40* and that has dropped the blowback through the inlet valves down to about 3200rpm and not really an issue on the track but a bitch on the road to and from the track...lol

[coxylaad]

Dyno time was had!

So the bike pulled pretty well right from the off and made 86bhp at the wheel.

The problem we had was the bike was popping and banging on the overrun and fast idle.

the carbs had 150 jets in them, and we had an option of fitting 152 and 155 jets. We tried the 155 jets, and it produced 88bhp, but it was massively over fueling on part throttle. I am not a carb expert, and I wasnt sure whether or the main jet will have an effect on part throttle operation, but it seemed to, so I went back to the 150s, and ended up with the fuel screw at 3/4 of a turn out, and slow air screw at 2 turns out.

Bike pulls really clean at WOT, but on the overrun it was spitting flames out the exhaust.

holding the bike at 4000rpm on the rollers it seemed to have a misfire. we managed to reduce it down but we couldnt get rid of it.

We called it a day and pulled the bike of the rollers, and for crack I rode the bike across the yard. It pulled clean with no hint of misfire anywhere.

I suspect it may have something to do with the inertia dyno, holding it at constant revs the throttle is virtually closed. Either that or we are getting fuel leaking through the carbs somewhere.

anyway it will get its chance on the track on Friday!

[cobbadiggabuddyblooo]

How did you go with your ignition timing???
If you've stuck with the default map just with the TPS turned on, you may find advantages in advancing the timing curve in that 20-80% mark that slowly tapers down to your full throttle curve with the FCR's.
The Throttle % is set up for CV carbies on default.

Try dismantling the exhaust and place some roof n gutter sealant on all the joins and put it back together. Perfect exhaust sealant and is well and truly up to the task and heat produced.

If you still have a lot of popping and banging, reduce your air screw by 1 complete turn.
It's a lot more sensitive after 1 turn as the needle comes further of the seat and allows more air in.
So 0.5-1 turn gives you only a very slight increase of air, 1-1.25 turns starts to gives you more, 1.25-1.5 give a good increase of flow and 1.5-2 gives you shitloads with the needle working its way well from the seat. Once you get past 2 turns it's bucket loads of air and you start to look at changing the main air jet. The 200 main air jet fitted is the largest they make for the FCR's and well up to the task for your motor.
Just check the pilot jets are 48's. I tried multiple pilots all the way down to 40 and still settled on the std 48.

The air screw has the most influence on the pilot and part throttle.
Stick with your 155 main jet and remove anything restrictive from the can. It looks like there's one in the photo. To get the most you want a healthy 55mm + straight through outlet especially with a 2-1.
One of the pro's and cons to a 2-1 system is you'll find a loss in horsepower around that 5000 rpm Mark purely due to the nature of the exhaust pulse.
If you have the chance to borrow a quality 2-1-2 exhaust, there is a good chance it will compliment the Kent cams better, don't be surprised if you find 5-6hp further gains from 3000 to 6000 rpm range which will benifit out of corners.
If your running the airbox, ditch the air filter it will love you for it too. Being a track bike the chances of taking in foreign matter is pretty slim with the air intake horn tucked right up in the tank facing backwards.
You'll find the needle clip position around the 3rd or 4th down from the top is a given for the OCEMP needle.
Float level from memory is 9mm on the trx and simple to set from the carb body with verniers to the top of the float just as the float needle seats itself.

[Mincehead]

I can`t read the figures.

[coxylaad]

there's no figures to read. that was the ignitech screen on the laptop.


One thing I didn't get was a dyno graph printout. in all the messing about with it it slipped my mind.

Track day tomorrow so it gets in maiden voyage! I hope it behaves itself for my dad.

[coxylaad]

How did you go with your ignition timing???
If you've stuck with the default map just with the TPS turned on, you may find advantages in advancing the timing curve in that 20-80% mark that slowly tapers down to your full throttle curve with the FCR's.
The Throttle % is set up for CV carbies on default.

thats interesting to know. I never actually did anything with the timing, we spent that long messing on with the carbs we didn't have time. Good info re the ignition retard, I can mess with that at the track tomorrow. whats the science behind that then? I thought you retarded the ignition with these carbs?

Try dismantling the exhaust and place some roof n gutter sealant on all the joins and put it back together. Perfect exhaust sealant and is well and truly up to the task and heat produced.

we have put a load of exhaust putty in there, it should be pretty well sealed. should be...

If you still have a lot of popping and banging, reduce your air screw by 1 complete turn.
It's a lot more sensitive after 1 turn as the needle comes further of the seat and allows more air in.
So 0.5-1 turn gives you only a very slight increase of air, 1-1.25 turns starts to gives you more, 1.25-1.5 give a good increase of flow and 1.5-2 gives you shitloads with the needle working its way well from the seat. Once you get past 2 turns it's bucket loads of air and you start to look at changing the main air jet. The 200 main air jet fitted is the largest they make for the FCR's and well up to the task for your motor.
Just check the pilot jets are 48's. I tried multiple pilots all the way down to 40 and still settled on the std 48.

we have 150 air jets. when we put the 155's in it was over fueling like hell on part throttle. and you are suggesting we richen the mixture more to stop popping and banging? there's flames coming out the exhaust on overrun!

The air screw has the most influence on the pilot and part throttle.
Stick with your 155 main jet and remove anything restrictive from the can. It looks like there's one in the photo. To get the most you want a healthy 55mm + straight through outlet especially with a 2-1.
One of the pro's and cons to a 2-1 system is you'll find a loss in horsepower around that 5000 rpm Mark purely due to the nature of the exhaust pulse.
If you have the chance to borrow a quality 2-1-2 exhaust, there is a good chance it will compliment the Kent cams better, don't be surprised if you find 5-6hp further gains from 3000 to 6000 rpm range which will benifit out of corners.

We have a baffle in the exhaust and we cant really take it out, as we have very tight noise restrictions at tracks in the UK.

If your running the airbox, ditch the air filter it will love you for it too. Being a track bike the chances of taking in foreign matter is pretty slim with the air intake horn tucked right up in the tank facing backwards.

no airbox, just blue trumpets and a big sock filter over both.

You'll find the needle clip position around the 3rd or 4th down from the top is a given for the OCEMP needle.

The needle is something we never really touched. We went on the basis that it was right before and the bike raced. I know I am putting a lot of faith the previous owner here - he might have been a complete muppet!

Float level from memory is 9mm on the trx and simple to set from the carb body with verniers to the top of the float just as the float needle seats itself.

9mm is what we have it set to.

[nr]

I'm busy taking notes here I noted the same thing on the shakedown run of my FCR equipped ex-race bike... a lot of popping and banging on the overrun. I haven't put it on the dyno yet, I noticed it on a long, downhill sliproad off the A14. If I kept the throttle completely shut, I could hear it quite clearly. If I cracked the throttle just a tiny bit, it cleaned up nicely.

Other that that, mine seems to carburate pretty cleanly. Next time I'm in there I'll whip the carbs off and take notes of the jets and positions. Will be interesting to see how close they are to yours.

[coxylaad]

Keep me informed!

always good to compare notes. I think at some point I will fit the bigger jets back in and see if I can get it set up, it did feel stronger in the midrange with them

edit just read your blog, we have had very similar experiences with them leaking petrol and stuff!

who would have carbs.

[cobbadiggabuddyblooo]

Your over rich part throttle is dictated by needle position.
Use your 155 mains but move the needle clip up 1 position so the needle sits further into the main jet.
The needle position is an easy task. Remove the 3 top cap head screws, you will see a bolt with an Allen key insert that sits on top of the slide. Just remove that and you can pull the needle straight out so its a 3 minute task on each carby.
You'll get the best of both worlds with more torque and horsepower over 3000rpm plus a couple of extra ponies at peak revs...
The leaner mixture on over run can easily be tweeked by screwing the air screw in . Try 1/2 turn less from 2 turns down to 1.5 turns which is back to the base setting.
Changing main fuel jet is another simple task accessed via the bung in the bottom of the bowl.
The carbies are designed for race application so quick easy access makes tuning easy.
As long as your A/f is between 12-13.5 you'll get good torque . 14.7-15.2 is just a figure where potentially all your a/f mix is being burnt. That doesn't mean peak torque/ power. It's a bit more of a figure suited to emission control.

Hope this helps...
Hope the weather is good for your trackday..

[coxylaad]

weather was good. bike carburation blew goats.

it seems ok on full throttle through the revs, but it bogged and hunted all over the place coming on the throttle.

going from a closed throttle back onto full throttle at 7000rpm was causing it to hesitate, same at 4000rpm.

part throttle generally felt a bit woolly.

We are going to bite the bullet and pay a guy to have it set up properly.

on the plus site despite the fact the bike was running a little rough the bike was an absolute hoot ride. so much so I am considering selling the fireblade and putting my trx back on the road.

whats a safe rev limit on the trx? the pulls hard all the way round to 9000rpm with seamingly no power drop.

[coxylaad]

my only session of the day on the TRX:
https://youtu.be/hX8DIxS58xM

was a lot of fun chasing down faster bikes.

[nr]

Nice! I've never ridden at Croft - after watching that I'm tempted to give it a whizz sometime.

What happened at the start of the 2nd lap? Did it jump out of gear? Or was is the old bugbear of swapping from road pattern to race pattern shifting?

[Mincehead]

Several `jumped out of gear` moments, they all do that! I like Croft too, crackin circuit but suffers from `we live next to it, arseholes` syndrome sadly.

[coxylaad]

Nice! I've never ridden at Croft - after watching that I'm tempted to give it a whizz sometime.

What happened at the start of the 2nd lap? Did it jump out of gear? Or was is the old bugbear of swapping from road pattern to race pattern shifting?

It was a bit of both -my blade runs race shift and this is road. I had to pause a couple of times to make sure i was going in the right direction, but the main problem I had was the gear lever was too high and I wasnt providing a positive enough shift. once i made more effort it was fine. I wouldnt expect it to jump out of gear normally, this was rider and setup problems

couple of vids of early on in the day on the blade if you are interested:

https://www.youtube.com/watch?v=Yn2z2hS2mfk&t

https://www.youtube.com/watch?v=JHpUsRVwqAg&t

i lose out a shitload in the braking areas to the fast guys, I need to tighten that up.