Author Topic: Performance problems (Read 45379 times)

Lefty · « **on:** May 19, 2015, 07:34:31 pm »

my FT is bogging when opening the throttle quickly, I first noriced it a couple months ago, it would bog in 3rd & 4th gears when I'd open it up. The performance, since I rejetted, modded(set on fire, haha) the OE air filter & replaced with green foam, thumperstuff header & SuperTrapp can was amazingly spot-on- no backfiring on decel & plenty of giddy up, no matter what.
It's getting a little worse with the warmer weather.
I feel it's getting too much fuel when I lay into it, so i'm wondering if I should go down in size with the main jet, or should I move the clip on the needle(up? Down?),any help would be appreciated, Lefty.

wrk2ride_ride2wrk · « **Reply #1 on:** May 20, 2015, 10:30:43 am »

you might want to check inside the slide, the screw in there that holds the needle in position may have worked loose or even unscrew'd completely

I have
#58
#155
25 thou shim

and its magic

triguyracer · « **Reply #2 on:** May 20, 2015, 12:36:14 pm »

I have just about the same jetting 58 pilot and 25 thous shim under the neddle and a 180 main jet with a white brothers pipe with a supertrapp with 5 discs uni foam filter without the airbox works xclnt good throttle response everywhere and pulls good to red line.this is with a stock motor no other mods to the motor

WTF304 · « **Reply #3 on:** May 20, 2015, 04:11:01 pm »

I'm having the same issue.... she doesn't like WOT in 3rd - 5th. It's almost like she spits instead of bog .... I've got a 55 pilot and a 160 main. Does shimming the needle really make that much a difference? And if you find your problem please keep me informed. ....

Lefty · « **Reply #4 on:** May 20, 2015, 05:24:26 pm »

Shimming the needle, how do I do that?

triguyracer · « **Reply #5 on:** May 20, 2015, 08:05:16 pm »

Shimming the needle does make a difference,the best way for me was to pull the carb this way it made removing the slide less of a problem,take the slide out and on top in the middle there is a round white plastic piece that is the stopper for wide open,you pry pull this out be carefull as it is plastic and you don't want to brake it,when this piece is removed you will be able to look down from the top and see a slotted screw,undo this and lift out the needle ,just turn upside down and it will drop out.Now find a washer to fit on the needle below where the top spacer on the needle is,I used a washer from home depot just make sure that the outside dia is the same or a bit smaller than the spacer that holds the needle if not it wont drop down all the way and your bike will run to rich,probley wont run if you don't make sure it is as small or smaller than the one on there,I had to file and trim mine by hand to make the outside dia right.The washers I used where 25 thous thick these worked real well.Some times you will be able to find very small washers on small electronic stuff,just don't over do it on the thickness a very little makes a big diff

Lefty · « **Reply #6 on:** May 20, 2015, 08:17:28 pm »

Thanks, I'll start looking for washers.
I remember reading about the different "circuits" of a carb- the pilot is idle and the main & needle circuits are 1/2 to 3/4 throttle and 3/4 to WOT, right? So the main is 1/2 to 3/4 & the needle is 3/4 to WOT, right? I'll post up my results.

scottly · « **Reply #7 on:** May 20, 2015, 09:31:58 pm »

Shimming the needle didn't make much, if any difference, with a free-flowing air-filter. With a stock airbox, it shouldn't be required at all. What size jets are you running, Lefty? The common set-up with the airbox seems to be a 58 with a 145?

triguyracer · « **Reply #8 on:** May 20, 2015, 09:44:25 pm »

The needle is from about one third throttle to two thirds the main is a little over half throttle up to wide open they overlap to a certain degree.the needle is the midrange and the main is half or so up to wide open

scottly · « **Reply #9 on:** May 20, 2015, 09:57:46 pm »

The issue with a CV carb, compared to a conventional slide carb, is that the slide (and needle) position isn't controlled directly by how far you twist the throttle; you have no idea where the slide is. From my testing, the slide is fully open by about 3500 rpm with a free-flowing air filter, requiring the large main jet. With a stock air-box, the CV carb acts very differently, and requires a smaller main.

triguyracer · « **Reply #10 on:** May 20, 2015, 10:16:40 pm »

yes but there is still a butterfly in the carb that is attached to the throttle the air flow is still partly controlled with the butterfly,the slide can be wide open but you still have the restriction in the carb depending on how far open or closed it is.allowing the motor to only take as much air fuel that the motor can take,the only circuit that I can see that over rides this is the accelerator pump and that seems to be just of the bottom of the rev range,am I missing something

Lefty · « **Reply #11 on:** May 21, 2015, 07:13:58 am »

I'm running a #145 & a #58, as suggestef by J6 here ,I also got rid of the original paper filter & replaced with green a/f foam, so I'm running with the stock airbox, but a free-er flowing a/f.
The 1st season with all mods the bike ran out perfectly, i haven't clocked 200 miles since then, and now it's bogging in all gears if I really punch it.
So I'm guessin I should start by going down in size on the main jet? Also, where's a good site to order Jets?

J6G1Z · « **Reply #12 on:** May 21, 2015, 07:33:10 am »

If the bike ran fine in its current configuration last season & nothing has been changed, I'd try running a tank or two of Seafoam through it & see if it doesn't clear up. http://seafoamsales.com

After that, I'd try changing the spark plug for a fresh one.

Something else to consider... Possibly the rubber diaphragm in the carb has dried out & has a leak in it. Here is about the best FT Ascot carb rebuild kit out there. http://randakks.com/collections/honda-ft500-ascot-single/products/ft500-ascot-randakk-master-carb-overhaul-kit

Other than that, its trial & error time with the jetting. You might try SUDCO for jets & guidance. http://www.sudco.com

There are some jetting guidelines for Mikuni carbs stickied at the top of this section. Mikuni & Keihin use different jet sizing schemes so it would be a rough guide.

Good luck.
J.

triguyracer · « **Reply #13 on:** May 21, 2015, 09:22:57 am »

another thing to check is your spark plug cap almost all bikes from this era used a resistor spark plug cap,they do go bad and can be a very difficult to know they are bad and can cause many of the problems you have,spent many hours chasing down this problem on bikes when I worked in dealerships as a wrench,they don't go bad often but when they do they are a easy problem to overlook.cheap to fix though and a easy fix,it is one of those things that is just so easy to overlook and miss

Lefty · « **Reply #14 on:** May 21, 2015, 11:37:13 am »

Thanks for the advice guys, I will try Seafoam & have a look at the boot, I replaced the plug last year but I'll pull it & have a look. I'll also see if the intake is leaking.
I appreciate your input, Lefty

WTF304 · « **Reply #15 on:** May 21, 2015, 01:45:55 pm »

yea I've got the same issue but i have a larger main then you but my issue isn't as bad as yours sounds lefty. I'll probably leave it for now till the weekend and take my carb out, might just be some dirt or something

scottly · « **Reply #16 on:** May 21, 2015, 08:34:46 pm »

Quote from: Lefty on May 19, 2015, 07:34:31 pm

my FT is bogging when opening the throttle quickly,

Check the accelerator pump.

WTF304 · « **Reply #17 on:** May 24, 2015, 04:20:43 pm »

I found the fuel line was swollen by the carb and was leaking.... think that was my problem but i also removed the snorkel tube from the filter, that could have just been irrelevant. No more issues with WOT now, just a little at mid range, also that could be the snorkel tube removed doing that.

But i figured i should report it incase it's something you might now have noticed

WTF304 · « **Reply #18 on:** May 24, 2015, 06:12:42 pm »

Not have *

Lefty · « **Reply #19 on:** May 25, 2015, 04:58:14 pm »

That's a coincidence, I had a similar problem.
The smaller line from the petcock had a little crack in it. I replaced it & the bike runs out great now.
Thanks for all the info guys.

WTF304 · « **Reply #20 on:** May 25, 2015, 06:39:54 pm »

That's good to hear that my problem was your problem lefty .... a very simple, often overlooked problem.

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Author Topic: Performance problems (Read 45379 times)