Dyno Chart for '99 FE501 with FCR41

jmosher · Nov 4, 2020

I recently posted this '99 FE501 with a FCR41 for sale, and I thought some people would like to see a current Dyno/AFR chart for this bike. I am a tuner with my own Dyno for my Land Speed race team. I know the FCR's very well, and I spent an afternoon dialing this bike in. It has a "Big Gun" pipe as the only other engine mod.
I am at 7,000' elevation in Santa Fe, NM, so the jetting will be leaner than Sea Level by (2) steps. I use 4th gear, because it is closest to the 1:1 gear ratio, and gear drag will be reduced from an OD gear (5th or 6th). Plus, since we have 20% less air, the power typically drops off by 25% (cam efficiency drops with elevation). So, add back right at 33% more power than I show here for Sea Level.
I kept the average AFR at roughly 12.5:1, so I have some safe range down to 3,500' elevation, and up to 10,000'. It would make max power with 13:1. I used a 148 Main jet, and a 45 Pilot for this 7,000' test, but a 152 Main, and a 50 Pilot would be best for Sea Level. The mixture was best at 1 turn out. These numbers should be good for 450's up to 570's in my opinion. Enjoy!
Here's a pic of my "Twin-Scout" Altered-Vintage Land Speed racer. Dual engine, 80 year old Indian Scout motors, 240 Hp/187 Tq, and 177 MPH on the salt. It has set 14 new records. Notice the FCR41's?

383hq · Nov 4, 2020

I love mad, ingenious ba$tards.
They make the world a better place IMHO

Thanks for sharing.

Taffy · Nov 5, 2020

jmosher said:
I used a 148 Main jet, and a 45 Pilot for this 7,000' test, but a 152 Main, and a 50 Pilot would be best for Sea Level. The mixture was best at 1 turn out. These numbers should be good for 450's up to 570's in my opinion. Enjoy!

well done mate and thank you for that. I've been running my SOP dyno for years and my sea level 400 ran a 148MJ and the best oif my tuners are down there too.

that PJ is only like that because of the needle design whereas the MJ is reliant on itself.

regards

Taffy

thorgan · Nov 5, 2020

Hey jmosher, I'm curious to know what needle you've got in there (and at what clip position). As Taffy hinted, these engines seem to be quite sensitive to the needle, often requiring changes to other jets to compensate for poor needle choice. I've probably got 30 or 40 needles in my "collection" from trying to find the sweet spot for one of my 600's and I'll be sorting an FCR for a 2001 501 (being punched out to 522cc) when Thumper Racing is finished with it. However, I never had the benefit of a dyno and I'm sure my butt isn't as sensitive as Taffy's who's jet kits, in my experience, have been quite good.

jmosher · Nov 5, 2020

Some FCR tuning

Actually, I don't know which needle is in this '99 FE501's FCR41. It was bought new from Sudco, and is likely the stock needle, and clip position. I will pull it apart the next time the gas tank comes off. Usually, Keihin made the best choice with their original needle. Needle swapping can drive you crazy, because the change in feel is so subtle. I've found it best to leave the stock needle in there, and try the various needle clip positions. This is done after you have found the perfect Main, Pilot, and mixture settings. Then move the clip to a lean position, and test ride the bike in the mid-range, like slow city traffic speeds. If the power feels somewhat flat, then richen the clip position. Test it again. Once it feels crisper in power, stop there. You can continue to richen the needle, but you won't feel any difference as it gets richer. You want the first position richer than the lean flat feeling. You need to drive test a needle position for several miles to get a good feel for the position.
On my dyno, and can drive test it through the gears gently, where I am in the needles mid-range, and watch the AFR numbers closely. I want to see between 12.8:1, and 13.5:1. I go through the gears (3) times. One slowly, one slightly harder, and the third, a bit harder. Then I can average all (3) tests to get a feel for the AFR achieved from the needle's clip position. On this '99 FE501, I was right in the middle of these numbers, so I didn't have to look at the needle.
To determine the correct Pilot jet size, you need to adjust the mixture needle to find the fastest idle when fully warm. First you turn the needle in till the RPM starts to drop. Then turn it out till it speeds up. Keep going till it starts to slow again. Turn it back in to that fastest idle position. If you are at, or very near (1) turn out, then you have the correct jet. If you are at below (1) turn out, then the Pilot is too large. If you are at above (1) turn out, then your Pilot is too small. For Amals, Mikunis. or DelOrto's you are looking for 1 1/2 turns out for fastest idle.
The main jet can be tested by the stop watch method by using a taller gear, like 5th where you can start off slow, whack the throttle fully, and time the run over a measured distance. This must be a repeatable test with the same marked off distance, and entering the start point at the exact same speed and RPM. Use a helper with a stop watch. The quickest time will be from the most correct main jet, which will be making peak power (and best AFR). Hit the throttle fully at the entry point, and have your helper, who is standing at the finish point, start the timer when he hears the motor rev up, and stop the timer when you cross the finish point. This will get you very close. This should be helpful to many of you. See Ya; Jim Mosher

thorgan · Nov 5, 2020

Hmm...found a document at Sudco that indicates they use an "OCEMR" needle. Not sure if I have one of those since I'm cheap and buy used carbs off of ebay. Maybe I'll pick one up and give it a shot on the 522 when it's done.

Thanks for all of the tips, Jim!

steve · Nov 5, 2020

After the main, the needle is the most critical thing when tuning an FCR in my experience. I fitted and FCR39 years ago to my FE501 using Taffy's jetting as a base and it went well enough by SOP. Its hardly ridden now, but has always, post FCR, been an absolute PITA to start from cold, whereas hot starting is fine.

I acquired another FCR an MX aka Mk2 to adapt and its stalled work in progress.

In the intervening years I've got into DR650s for adventure riding, and recently sold my FE650, so my '98 501 needs to get operational again.

My DR650s have gone through FCR39s, 40s and 41s which I've set up with an O2 sensor and wideband AFR meter. The interesting thing for me was that the 39 and 41 had a happy spot with the same needle, whereas the 40 needed a different needle to get it right. I've got about 25 different needles in my shed, and there must be few hundred available.

The needle is critical to getting the part throttle rideability right, and makes no difference on a dyno for the most part.

Which means I'm curious what needle is in play, like Thorgan.

Taffy · Nov 6, 2020

Well Thorgan, he doesn't know what the needle code is so the only bit I can admire is the MJ size which is all a Dyno is there for. Even he says he finds needle shapes confusing. I used to but because SOP is free, I did my learning there.

as for EFM, go look on a chart and it is basically THEE richest, THEEEE Thorgan, THEEEEEEEEEEE richest needle you can fit. now if we work on the basis that rich is dull, rich is safe, rich is passive, rich has no coughs, splutters just **** to start warm, other than a few pops on the overrun, what do we do when we admire EFM?

I mean, I saw a window licker once open a door, do I admire him and follow him?

NO.

so a 50PJ isn't "the business". Nor is an EFM.

I just sent my new needle to the States. I was really looking forward to it being tested by what seemed a reasonably competent bloke with a KTM 660 LC4. he was one of the few in 10 years to write in.

out of 600 jetting kits;
585 x nothing, nada, zilch, phuq-all, not a sqweek.
10 x i want my money back you C**T
5 x feedback

of those 5;
3 x "it ripped my arms off.... = so your kit is only therefore just 'OK', and better than walking home...but only just"
2 x sensible feedback.

So let's be mindful of the fact that a trip to Thumpertalk reveals that all Americans are running 170+MJs even in 250s and the jet goes up as the CC gets bigger.

The KTM rider just got the following results in August;
My new design of needle
145Mj
clip 6 (not the usual C7)
32.PJ

at each stage over two months we worked his jetting down and down and it went quicker and quicker. and i was getting one off words and phrases like 'best ever', 'OMG, wheelies in 3rd'. I could go on and on. everytime he said "surely that is it" I said "no, I'll send you this for free" and he fitted it and then he'd say "way to go dude!!!!".

so I asked him at the end, now that I'd worked with him for two months and sent him stuff for free and his bike was a rocket; "would you write me a paragraph on your bike?" "sure dude"

"brilliant" I said.

"Taffmeisters new needle has improved punch at 3/4 throttle. Taffmeisters jetting kit along with the available jetting advice has allowed my bike to start easier, run smoother at lower rpm and rev higher all while using less fuel."

there you go, the most wooden ******* awful piece of unusable junk I've ever seen.

sounds like one of those Communist leaders in the third world.

This whole showe is Phuqed I'm telling ya

Taffy

heidenberg · Nov 6, 2020

Gotta get one for the 600, maybe try this 39slant on the 501

steve · Nov 6, 2020

ACtC-3dpxSGYAxmU9sPxLo9gN5tGpYOloJr-Nv0Dvo_g3HL8b9pxMeBsi2l_ER61sOFQYisuxWhJt2aQeU6XA_7osvgckBUEW_vZ7CADQq66935CUUe_KctDLCsX1YGEh6LrbqpdEMG45_W590hqX0PUqb6Z=w594-h800-no

If you look at the above graph, you'll see that the needle is critical from 1/8 to 7/8 throttle, diameter, clip and taper, and where the taper starts, and then there are the dual taper needles too, like I understand Taffy's to be. One size needle does not fit all.

Taffy · Nov 7, 2020

I'm afraid that that graph is wrong Steve.

I can go from a 175 to 160MJ and need to alter the pilot screw a lot, almost enough to need to change the PJ. So the main jet has an influence down to idle.

the jet needle diameter is just total bollocks. Just go out to your bike and put an * * M in and start it, it will blubber. then thange to a * * S and you'll have glowing headers, it'll pop and bang. So the JND is totally wrong and should hit the side wall at the same height as the PS/PJ. that should come down and they should start together.

the slow air jet is wrong. it is the slow air jet that carries the fuel from the pilot. a bit like you getting in my wheelbarrow Steve and I give you a lift. as long as I keep lifting, you keep delivering so the Pilot air should stoip when the pilot jet does.

the jet needle taper fades away much earlier, it's nearly useless at half throttle.

I'm not sure how you would draw the needle clip as it is a moving part. maybe it should have been done as a band of grey? anyway, put a needle on C1 and start it and then put it on C7 and start it. the bike might not even start! yet apparently the needle clip has no influence at idle?

the whole thing is bollocks Steve and if you believe it your going to hell in a handcart.

I don't mind telling you Steve because I know you but guys like - others - never admit they lose/wrong (DJT) and just lurk, and lurk and lurk and at the end the last thing they do is say; "oh fair do's, you taught me something" they just wait to cause **** a mile down the road.

actually I might use a DJT. its fat, has a late start, finishes halfway, has a lot of papping and banging, makes an awful racket and wants throwing away as soon as possible.

Taffy

steve · Nov 7, 2020

Its a guide Taffy, put out by Keihin, the designers and makers of the carb. I may not have the tuning experience that you do, but I've played with enough FCRs, and in recent years, with an O2 sensor and wideband AFR meter to have a decent feel for them. People who ride my FCR'd bikes reckon they work better than theirs.

Look at the graph again, everything overlaps at some point, the challenge is getting the balance right, and in my experience, the needle is critical to that end. No one needle fits all FCR applications, else there wouldn't be the 100 + that's available.

steve · Nov 7, 2020

I should add that I agree that a too big main can influence idle, that's why you have to start with the main first. Once that's right, its influence lower down is as per the graph. The graph assumes the jetting is close to right.

Taffy · Nov 8, 2020

steve said:
Its a guide Taffy, put out by Keihin, the designers and makers of the carb. I may not have the tuning experience that you do, but I've played with enough FCRs, and in recent years, with an O2 sensor and wideband AFR meter to have a decent feel for them. People who ride my FCR'd bikes reckon they work better than theirs.

Look at the graph again, everything overlaps at some point, the challenge is getting the balance right, and in my experience, the needle is critical to that end. No one needle fits all FCR applications, else there wouldn't be the 100 + that's available.

well, if we're going to talk about people riding bikes I've got over 600 on mine now. so let's stop there.

My needles have a 4 angle change now plus straight so you might call that 5-angles (4 changes). i've so much experience now, I just ask for the needle straight width and try and work ther PJ down to join it. the question then becomes either/or;

lots past the needle and small PJ
even them up
minimum past the needle and the rest in with the PJ

with the 4 angle taper you can't go wrong, all you need is the needle straight to be right. if someone is stuck on a 42PJ then cut some slack on the straight and they can try a 40 or 38, or 35.

the latest needle I have made meant that my Yanky chum got down to a 35PJ/60PA and it took him so long to get the 50PAJ to go with the 32.5 I sent him that the Autumn had come. But I think he'll hold a 35 all Winter. I will ask...

I'm convinced that the needle is the sponge and the PJ is the cream, jam and icing....just that little add-on = the sponge is the filling = the PJ you can control. yet if you look at that chart the needle is doing nothing low down.

If people don't think the needle is working at idle; block it off and see what happens!

That chart isn't right Steve and you didn't jet your bikes following it. If what you said was true (about Keihin) , why did all the early Yams come with the "maximum" MJ at like 175 or even a 180, PJ at 48, 5 second squirt, and the needles were rich too. how come, two years later a KTM had the same jetting? (still rich). They also did totally the opposite with their air jets and put the "maximum" in as well (which = "opposite affect") when everyone got a 100PAJ and a 200MAJ. They are on 115 nowadays, some difference.... and on exactly the same bikes - whacko!

I suggest that far from testing them, the factories took Keihin's first settings and then worked gently and safely to as far as they dare (which wasn't far!).

think and draw a 4-angle needle on paper with the first being a C. It can't go wrong really, it cuts out mistakes.

why in the end do the manufacturers make their own needles and their own jets? the smallest PAJ for the later OEM/Proddie carbs is an #80 so Yamaha and Honda had to go out and have smaller PAJs made in #50, #60 and #70. and what about needles? Keihin never made a 'C' needle so Honda and Yamaha had to have them made......

So what to make of Keihin? That chart you put up just confuses people but you are covered "....because keihin did it". But it's not helpful though is it.

It was me that first put up the PA to PJ ratios in 2001 and I might have to be the one that draws....cake!

that "DJT" got chucked out yesterday - while on the golf course. what a great day for the world, hopefully it's never coming back.

regards

Taffy

Alfy · Nov 8, 2020

That graph is neither right nor wrong. It gives an idea of what to modify based on the position of the accelerator. Since the driver circuit and the main circuit are two distinct circuits, I believe it is more appropriate to have 2 graphs, one for each circuit. And also a third graph for the pilot screw which is located beyond the vacuum valve and which is fed by the idle circuit but also has a "screw regulator", a tap. However yes, if I change needle diameter 1 size I have to change the PJ 1 size

Taffy · Nov 16, 2020

The last time "Daddy" had someone draw him a picture was how long ago Steve???

or should it be; :cry::cry: as it was at the time!

Just for you....

Taffy

steve · Nov 16, 2020

Not sure of your point Taffy, graph looks similar, not identical, but close enough to guide tuning along similar lines.

heidenberg · Nov 16, 2020

All these graphs, just put a wideband 02 in the exhaust with datalogging and get on with it..otherwise you are just pissing in the wind

steve · Nov 16, 2020

Agreed, but the graphs guide you as to what to change to improve the AFR readings.

heidenberg · Nov 16, 2020

No doubt, considered that after I posted...getting to used to typing numbers into a laptop to change a/f

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Dyno Chart for '99 FE501 with FCR41

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