Got a horsepower Dyno run!!!

[audijunky]

Unfortunately(sp?) it seems my bike is only making 63 peak horses. I believe that is low for even stock.... right? Dude says I need some more work on my carbs. Whats stock HP around 90 ?
Anyways I also found out are bikes are faster than a 03 honda shadow sabre 1100. Little bit a good news.
I HATE CARBS. I have had problems since the beginning. Thank I am gonna do a complete tear down and cleansing again. Last week before the Dyno I had them Synced at a shop, but I still have low RPM issues. Unless everyones bike doesn't really get it untill after 3K rpms or so. However I know that is not the case.Whats the consensus? Is my problem carbs, or possibly exhaust/intake setup? I am running Pod filters with TCs velocity stacks, 45 pilots, and 145 mains, I am at 2 1/2 turns out on my mixture screws( when I did the sync we pulled the plugs and the tips were white sitting at 1 1/2 turns out). I am also running open headers with a bolt and washer style baffle(to create some back pressure) . Problems are sluggish up to around 3K rpms, and when it gets warmed up it backfires on deceleration, and also has problems sometimes while just cruising(sputters sometimes).

Need help, what should I do???????

[AlanB]

Hi Audi,

Our local dyno only ever ran three stock XS11s. Mine (with pipe) and another were both around 70 at the wheel, so you may not be so far out at peak. The third bike had holed diaphragms in the carbs and peaked around 27bhp........Customer declared himself happy with the result, did not need it to be any faster, and continued on his way..........

These bikes should pull from low revs, so you do need more work on the carbs; Possibly dirty pilots, but more likely just needing to get them sorted to suit your pipes and filters.

CV carbs need a restriction to create the vacuum to lift the slides. As a little experiment, try taping over about 80% of the surface of the pods with duct tape, and see if it goes better at the bottom end........ Remember, as stock, all the air for the four carbs comes through the "Trunk" on top of the box, so you won't strangle it at lower revs!

Let us know how you get on!

AlanB

[trbig]

Try taking off those pod filters and stacks off and run it around for a few minutes without them and see if you notice any difference. It should only take a couple minutes to get them off to find out. Yes, that is a low number for these bikes. I'm not too familiar with the stock sizes on the XS, but those mains are monsters compared to mine. Seems like you'd need plenty of air to take advantage of that.

You made it sound as if you pulled the plugs after you had synched the carbs.... like right after idling long periods. You need to take a spark plug wrench with you and get the bike warm, then run it above 4k rpm for a while... pull in the clutch and kill it and coast to a stop. Pull a plug or two and check them then... make sure you burn your hand sufficiently! This is checking the fuel mixture for the mains, not the pilot circuit/jets at idle.



Tod

[TopCatGr58]

Hey Steve/Audi,

HERE's the mondo dyno thread that we talked about our results a few years ago. Mine peaked at ~78 bhp and that was with a little big bore kit, but I might have been running a bit lean!?

If your plugs are that white, you might be a bit lean on the pilots, but like the others said, reading them is done under load on the road, not idling! With your dyno run, did they do an air/fuel mixture reading for you?? I didn't do one because I was "at the time" only interested in finding out the rear wheel BHP! Wish I had paid the extra for the AF ratio readings!
T.C.

[audijunky]

Hey guys
TC no I didn,'t do the air/fuel mix check either. Like you I wish I had paid the extra to get it done.
When I checked the plugs it was right at the beginning of the sync. Before that I had been running the bike down the freeway @70mph or more @ about 4-5 K rpm's for about an hour. SO I think the white may have been caused by the main cicuit. My Mech told me( he is a friend of mine who went to MMI and is certified through a few different Manufacturers so I dont think he would lead me astray) He said I should go up so more on my mains like 150. With the high flow intake and straight pipes he thinks its starving. While doing the sync we turned my mix screw out another full turn putting me at 2 1/2 turns out and she started purring like a kitten. Sync went good, I watched and all four were inline(MERC sticks). But she still stumble off the line up untill around 3k.
Heres some more info on what has been done to the carbs. The original #1 and #2 had a stuck miture screw so had to be drilled. these two forever ran rich. bought another set off here and both of its #1and #2 were drilled also(damn it) so I converted #3 off bought set to #1 and #4 to #2. Had to drill a hole in the body of #4(new) to insert the vacuum advance brass tube off #2. Then used a 1/16 drill to penetrate into the carb throat. Actually worked out really well. Hole is the same size as the original hole in #2 and I switched the butterfly from #2 (old) to the new #2. I also checked the newer( to me) carbs for needle set position and the diaphrams for holes or cracks, and I also switched out the floats. Now none of my carbs have been drilled out. I am running 45 pilots and 145 mains. One thing I didnt do is clean the new #1 and #2 really well. That will be the next thing. Take them all apart again and do a complete and thorough cleaning. However I do no think this will do anything, cause everything I have done this far has not helped the low end stumble.
Thanks for your advice gentlemen and possibly ladies

[petejw]

Hi audijunky,
Does ur low end and mid range feel flat
when accelerating as well as the stumble?

You'll find having the open exhaust can
cause this, the bolt and washer thing is
insufficient IMHO for good back pressure.
Im running pod filters as well.

I was running a similar open muffler
and the difference with the low and mid range
pull was huge when i began playing around
with the baffles, I also had the stumble down low
that is also gone.
If ur going to be riding at high
revs all the time then the open system would b ok.

have you got another exhaust to play around
with or a muffler u can attach.

Also 2day I was mucking around with the diaghram
springs I know its been mentioned before, but i cut
out 9 coils on the spring and wat a difference that made
to the pull down low and mid range, if you do
trim the springs start of small, and experiment, my diaghram rubbers are prety shot so it would take more vac 2 raise them.

[audijunky]

Thanks for the advice Pete
I currently do not have any mufflers, but hopefully a friend of mine is going to let me borrow some he took off his Valkrye.
My diaprams are not worn out but there is some slack for lack of a better word when they are installed. In other words the boots are not tight from the cylinder they are attached to, to the top of the carb. Do you know what I mean? I am gonna check and see what the other carbs diaphrams look like and if they are better I will use them. If that and the mufflers don't do anything i am gonna look at the springs.

And yes, the problem is in the low end wether I am wide open throttle off the line or just cruising at low RPM or if I am just slowly rolling on the throttle.

[petejw]

Definately do the muffler thing,
id hold back on the springs on the carbs
till u get everything else sorted out first
or u mite create other problems for yourself,
also if ur putting muffler/s back on u mite wanna
go back to original jetting otherwise she'll b way
to rich.

with the diaghrams i think i know wat u mean,
if they arent secure at the base could they b leaking?
this could also cause the bike to bog down.

Harleys have the same problem with the open
headers they loose there low down and mid range
torque, thats y u always see them in ur rear view mirror. lol

[TADracer]

Hey guys,

Reading this thread I thought I would throw my $.02 in.

I have a 79 special with pods, MAC 4-1 header, Dyna coils with Accel 8.8mm wires and all else is bone stock. I experienced the stumble and flat low end performance. It is caused by nothing more than an imbalance of parts. I played around with modifying the baffle a bit and also running with the baffle out. Doing this reduces back pressure and has a definate flat effect on low/mid range performance but high end it is a bear. However, I do little work over 100 mph! So I put the baffle back as it came from the manufacturer and tuned the carbs from high to low as described in the CV tuning article (I think there is a link somewhere on this forum). With this method you find the correct mains first, then the needles, then the pilots and then the idle adjustment screw.

I ended up as follows: 145 mains (stock 137.5) 45 pilots (42.5 stock), needles in mid position (stock), Spark plugs NGK BP-5ES (BP6ES stock). Everything else is at the factory settings.

Set up like this, my plugs burn tan when I check them after running at any RPM under a load (I carry a nomex oven glove when I check plugs so I dont have any burnt fingers). My machine will come off of a stop in first by just letting the clutch out slowly and will accelerate smoothly and hard through the red line with no problem. That annoying sputter around 3000 rpm and popping when decelerating is totally gone. Takes a bit of tinkering but this method works.

[audijunky]

this the article you speak of>>>
http://www.factorypro.com/tech/carbtun.html

I have tried this and believe I 've got the top end right.
I have got the same setup(jets, needle postion, pods) as you except for the pipes.
guess I am gonna have to put on some mufflerss. didn't really want to cause the bike sounds awesome now, but I want it to run right. Thanks for all the advice and I'll keep ya posted

[petejw]

Thats the site, ive also done my carbs
that same way with good results,
Im also running a hotter plug only
cause my rings arent wat they used to be,

another thing i found useful with mucking around with
the carbs is that if it runs better when cold than when
its hot then its running rich, and vica versa for the
opposite, if the bike runs as well both when its cold
and warmed up then uve got the carbs sorted out pretty
well.

my bike also sounded awsome with the muffler set up
i had, she literally sreamed at the higher revs but was
flat as a tack otherwise, ive stuffed sum wadding in the muffler
shes a lot quieter, butbig difference in the mid and low end,
and i have also noticed a bit of a decline in performance up top.