My Bemsee dyno results

scooble · Post by **scooble** » Wed Aug 08, 2012 9:37 am

here are the dyno curves from my bike, which felt quite down on power (even on the Bemsee dyno);

.....oh, and most of the (pattern) stem seals on my NC30 are leaking - Arse!

Luders · Post by **Luders** » Wed Aug 08, 2012 9:57 am

what is wrong with it?

scooble · Post by **scooble** » Wed Aug 08, 2012 10:10 am

I suspect that the R/H cyl had blown a crank seal as there was about half as much gearbox oil in there when I drained it (plus it was very runny - suspect fuel bypassed the seal when the carb over flowed).

Luders · Post by **Luders** » Wed Aug 08, 2012 11:11 am

are you using 28's or 35's at the moment?

scooble · Post by **scooble** » Wed Aug 08, 2012 11:24 am

started on the 35's using 155, then went down to 152.5 then ran out of jets so switched to the 28's.

Started off with 140 and the AFR was around 10. Switched to 132.5 and was around 12 ish. Considered that the airbox might be restricting it, so removed the lid and ran 150's to get the AFR back to about 12 again.

Luders · Post by **Luders** » Wed Aug 08, 2012 12:27 pm

has there been any modifications made to the ports on the barrels?

scooble · Post by **scooble** » Wed Aug 08, 2012 12:36 pm

they are the same KR1 barrells I have been using on trackdays for the past couple of years, but were tuned by Bob Farnham last year and I've only done one trackday and one meeting on them. The top of the cylinders were skimmed and the head machined so that the combustion chamber is 'sunk' into the head.
Prior to the tune, I always felt a strong pull from about 8k, however after the tune, I never noticed this 'kick' - I assumed that the tune had smoothed this out.

Luders · Post by **Luders** » Wed Aug 08, 2012 1:54 pm

scooble wrote:I always felt a strong pull from about 8k, however after the tune, I never noticed this 'kick' - I assumed that the tune had smoothed this out.

Sounds like it's done just that. Do you have a different top end you can try?

scooble · Post by **scooble** » Wed Aug 08, 2012 2:03 pm

the cases, crank and top end is with Bob right now, I did get to install a (spare) standard engine though, but it only lasted 3 laps in the pissing rain before the gearbox exploded!
I''m a bit scared to look inside, though, I do have a spare gearbox which I could fit if the cases aren't too mashed

Luders · Post by **Luders** » Wed Aug 08, 2012 2:16 pm

Do you think you'll be able to get that engine which is away at the moment on the Dyno before the September race?

I think you should have a look inside that one you had the gearbox fail on you.

scooble · Post by **scooble** » Wed Aug 08, 2012 2:22 pm

I know.....but I'm a bit squeamish

dave32 · Post by **dave32** » Wed Aug 08, 2012 2:30 pm

Hi Scoobie,
Are the powervalves working exactly as they should?
Just over 40hp is not right,if the vlaves are left in the low end position(below 8000rpm) then they only give about that.
What exhausts are you using?
Many years ago i had Bob Farnham "race tune" my B2,i wish i hadnt,it went from a flier that would red line in top on stock gearing to something that wouldnt pull top gear no matter what revs you went to in 5th,even running lower overall gearing didnt help.
After playing with different carbs,jetting,airbox,no box,3 sets of pipes,different ignition timing etc etc i had enough.
I took it to a guy who tuned my MX bikes,he had a look and all that had been done was the exhaust port opened right out,the barrels skimmed so now the powervalve collets had to be machined down and thats about it. =D>
Apparently this is typical of what messrs Farnham and Stevens call a tune,he had countless Stan tuned engines that had the same treatement,a big gaping exhaust port so it revs but thats it.
Farnham worked with stan before going it alone and it appears he kept to the same thinking.

This also wasnt the only case i came across,a 375 race tuned lc,rd500 stage 3 and an rd150lc farnham race tune,none of these machines would pull top and were a nightmare to get running right.
Back to the kr,the Mx engine builder did some work to the transfer ports and flowed the cases,i got it back and it was/is an absolute missile on road and track,it pulls fine from 6 but takes off at 9 to 12 and will pull higher than stock gearing.
I ran this with stock B2 exhausts and airbox initially,later S pipes and finally went for pete gibsons blown race pipes,it worked well with all these pipes,i also ditched the rear half of the airbox lid as the with the stock carbs there is not much to be gained in junking it.
bear in mind this was AFTER someone had already "had a go" at the ports,MX guy had a look at some stock barrels i showed him and said he wouldnt have opened them up at all,you dont need/want BIG ports to get results.

if you have another set of barrells i would stick them on,i really dont think you want to tune the KR as such unless you get to a level where you are riding the wheels off it all the time,reliability,driveability and well setup suspension,tyres and brakes will make the most impact in lap times.
Hope you get it sorted as it seems you had a bad 1st race weekend,not something you want when it costs so much (time and money).
ATB
Dave

Luders · Post by **Luders** » Wed Aug 08, 2012 2:48 pm

I couldn't agree more with you there Dave about the top end.

I don't have any experience with Bob Farnham, but was thinking along the lines of what you suggested there, which has killed the power.

I am thinking you should probably look at sticking the top end off the one with the transmission issue and putting it on the cases you have away with Bob.
Just stick a base gasket round the bottom of the barrel and take off the excess material you see on the transfer ports.

See how you get on with that for the Saturday and if you're still not 100% happy, I'll bring down one of my motors for you to run on the Sunday.

scooble · Post by **scooble** » Wed Aug 08, 2012 2:58 pm

years ago I had a Stan Stephens tune on my KR1 and it made more peaky and less powerful, so the next year I got my KR1S tuned by Bob.
There was a considerable difference. Bobs tune had a much wider powerband and was much quicker at the top end. When I changed to the Stephens top end on the KR1S, it was back to being peaky and slow.
However, when Steve Kemp worked at Bob Farnhams, he really F@#ked my RGV!
It could be possible that Bob gave it to someone else to tune, or maybe his standards have gone down hill

mj43 · Post by **mj43** » Wed Aug 08, 2012 10:07 pm

Stock motor = 50hp
+
Flow the cases and set the squish = 56hp
+
35mm carbs = 58hp
+
a bit of porting = 62hp
+
Lomas pipes = 62hp but 5more hp mid range (seen 64 but 62 probably closer to the mark)

forgot
+
TZ pistons for reliability and reprofile the head to suit.

That is dyno pro horsepower - easy and reliable.

On 28mm carbs 135 jets with airbox
On 35mm carbs 155 main jets with airbox
jet sizes up or down a size depending on the weather.