oh dear never mind carry on

fred · Post by **fred** » Wed Apr 17, 2013 8:45 pm

think the 142,5 s was a tad lean ,did 190 odd miles ,i could tell looking back it felt a bit peaky(i always learn the hard way but i do learn and have more feel for it now

) ,will be back together tommoro ,just glad the bores sound

dave32 · Post by **dave32** » Thu Apr 18, 2013 12:38 pm

142.5 RD's?
If so there LEANER than stock/genuine 135.
Go BIG,work down til it feels good,check the piston/head then go UP 1 size.
For the road or even a trackday you DONT need to run close to the limit.
Did it lock up on WOT or when you shut off/rolled back?
if it was as you backed off the needle needs to be richer.
By the way,what oil are you running now?
Alll good fun,reminds me of my elsie days

soldier on.

fred · Post by **fred** » Thu Apr 18, 2013 1:57 pm

it was at the end of a straight flat out ish ,just before braking and changing down gear and it was running on 1, still running motul 800 which seams fine ,it didnt lock up at all ,so rode it home on 1 pot ,ile get there in long run cheers

dave32 · Post by **dave32** » Thu Apr 18, 2013 5:12 pm

you running the complete airbox lid?
Motul 800 is one of the best oils you can get,ive just been running it on my TZ (at mallory,road race version) on strip down there are no vertical wear lines on the front of the skirt which is something i always got with A747 (no mechanical failures with 747 though).
so were they RD main jets?

fred · Post by **fred** » Thu Apr 18, 2013 5:40 pm

yea ,ide run for a week on 145`s and kept checking the plugs ,n coasting to a halt ,and was just on the turn to digestive brown from black ,the rad could of done with a inch an half of water so was probably running a tad hot ,i think this would make it run leaner ,ile start with the 147.5s again as its only on road and yep rear of lid removed,at least i know where the edge is now ,luckily these are usable second hand pistons ,,,,ive got to save up and get a set to send of to poeton as ive found a matching set of kr1s barrels that need replaiting

mj43 · Post by **mj43** » Fri Apr 19, 2013 12:18 pm

On standard carbs I used 135 main jets on teh race bike with no problems.

At Bonneville I used 132 main jets and did multiple passes with the bike on WOT for at least 2 miles with no problem.

145/147 is massive unless you are running 35mm then you should be 152 to 158 main jets.

I always run a full airbox, though with pickup in the front from above the radiator.

I would check squish, head volume and water leaks especially if you say rad was losing a bit. Head gasket is a good tell tale of a leak - leaves a slight mark on the gasket, though my experience is that it is normally the back of the head that leaks.

fred · Post by **fred** » Sat Apr 20, 2013 2:45 am

it was left hand rad pipe from t head ,i was just forgetfull all it needed was turning n tightening up a bit ,it was pissing out on way back from prescott ,thinking back i ran bike to work n back for 5 year on standard jets with no airfilter ,i always use heldite on the head and never had problems,so 135 standard is go,145 rd is go , how do they callibrate jets ? a known viscosty on a time ? i asked a old workmate to measure some on smartscope but realised measurements dont work as it`s flow,

mj43 · Post by **mj43** » Sat Apr 20, 2013 8:38 am

OK if on rd then 145 makes sense. Personally I would stick with kehein (or however you spell them) jets. People using rd report problems more often then people using kehien or mybe I just noticed them more.

dave32 · Post by **dave32** » Mon Apr 22, 2013 12:47 am

Thats why i asked in my first reply what make jets you were running Fred,your actually running leaner with that setup than stock,look in the region of 150RD with a modded airbox and go from there.
nothing actually wrong with the jets just the flow rating isnt the same as keihin,most blow ups would be attributed to the user assuming a 140RD would flow more fuel than a stock 135,and not taking any notice even if the bike felt leaner and the plug was saying it was.
Bonneville is at very high altitude,around 4 to 5000 feet ABOVE sea level,which would call for much leaner jetting (less oxygen) than blighty even if held flat out for a prolonged period (which would call for slightly Richer than ideal jetting to prevent powerfade).
dont forget to keep all these pistons Fred,all part of the process.

mj43 · Post by **mj43** » Mon Apr 22, 2013 8:09 am

dave32 wrote:Bonneville is at very high altitude,around 4 to 5000 feet ABOVE sea level,which would call for much leaner jetting (less oxygen) than blighty even if held flat out for a prolonged period (which would call for slightly Richer than ideal jetting to prevent powerfade).

Yes that is what we thought. Prior to going out I bought jets down to 120 but luckily misplaced them so we had to do our first run on 132 which were the jets we dynoed in the UK (it was a hot humid day in teh dyno room when we tested). Bike ran fine?
Whilst you are significantly higher at Bonneville I think air is 85% of sea level, humidity is almost zero and temperatures are moderate (it is the reflected UV that causes problems to people but doesn't affect jetting). On top of this the ERC110 fuel is oxygenated so the overall effect seems to be that we can run UK jetting at Bonneville

dave32 · Post by **dave32** » Mon Apr 22, 2013 12:43 pm

Interesting,so the other factors offset the altitude,then again bonny isnt like anywhere else on earth from what i can make out.
lesson 1 Fred,never assume anything.

Dave

fred · Post by **fred** » Mon Apr 22, 2013 1:19 pm

i can only test, in engineering the saying goes if you assume you will make a ASS of U and ME, thats a old one from colledge

dave32 · Post by **dave32** » Mon Apr 22, 2013 4:12 pm

What needle position were you running anyway?

fred · Post by **fred** » Mon Apr 22, 2013 10:45 pm

it was second from bottom on 142.5 when i lost a bit of ally down the pipe,on the 145 now ime on second from top ,done 60 mile from Saturday and its freeing up nicely so will check the plugs tomorrow

dave32 · Post by **dave32** » Tue Apr 23, 2013 12:06 am

So 2nd richest (position 4) now you've leaned it 2 positions and gone up 1 on the main?
I dont know,but if it melted the piston i would have gone up to at least 150RD and leave the needle where it was,then work down if it felt too rich.
Dont get too (be all and end all of jetting) with the spark plug reading for road use,too many variables to take into account,just aim for a darkish (not black) colour (depends on the oil),then you know its safe if the weather turns a bit colder.
for what its worth,you can seize a motor by running the needle too lean,or confuse things by running a lean needle and using a too big main jet.
The needle covers more of the rev range than any other component so its as important as getting the main right for 90pc of your riding.
HTH
dont want to see anymore pistons for a few weeks at least Fred.