FIXED: new superhawk owner, running issue constant throttle
 

i have a 2001 superhawk, the previous owner has put a k&n filter, renegade exhausts and told me it has been jetted to suit.

it also has a race petrol cap (keyless) he said something to do with pressure.

When im riding along (it happens more above 4000 rpm) and hold at a steady speed it seems to lurch as if its being starved of fuel but as soon as i open the throttle more it goes away and is fine untill i hold it at its new speed, happens in every gear and at any speed, i can gently open the throttle and have no problems or even open it fast its fine.

Any ideas why it might do this?

Research k&n filters on here. They don't work well on VTRs.

Ahh okay, i do have the standard one, do you recommend putting the standard one in with the jet kit and exhaust as it is and trying?

It's a start. I would also recommend getting into the carbs to find out what exactly has been done set up wise.

i shall do, i read the standard pilot jets 45? should be left it and the main jets changed only and 4th position on needle? (im at sea level)

i did some research to try find out why it would be doing this, previous owner cannot remember what jets are in it so ill have to look.

Are they easy enough to get to? ive not looked at their positioning yet.

And so the journey begins!

If you can be patient - try one step at a time. Step 1 - replace the K&N with stock, ride and see. If you still have surging, clean the carbs - you might just be suffering from clogged pilot circuits.


When you have the carbs apart, check the jetting to see how far from stock it is.


By the time you have read 1,000 posts about jetting on this and other sites, you will learn that stock is pretty darn close to right (maybe a little lean on top), and there is no "universal" solution to jetting your bike, and in my opinion you have two choices - read on here and experiment, or spend $60 to $100 on a dyno with an operator who knows a bit about carbs and save yourself multiple iterations.

changed to standard air filter gonna take it for a quick ride and see how it goes.

oem filter put back in and its still doing it.

i read people change the pilot jets for bigger ones when they should be standard so ill check that next

can anyone give me a quick explanation of how to get to the carbs?
guessing i have to take them off to get to jets?
airbox out too?
all lines off petrol tank?

First get the tank off, disconnect all of the lines, remove bolts, etc.. Take pictures of this step if it's your first time so that you get the lines back on where they belong.

Airbox is next, more pictures here to make sure you put the stacks back where they belong. Use a good screw driver here and dont crank anything really hard, its a bit soft in there.

Now you're down to the carbs. Coolant will need to be drained as mentioned in the manual due to your heater lines. Then carefully loosen the boots, wiggle, pull, and remove. Be extremely gentle with the choke lines as you remove them, their fittings are junk (talk to jack flash about this, he'll set you straight with all kinds of goodies).

That'll get you to the work bench for cleaning and figuring out what your PO all did

brilliant thanks, sounds like a bit of a pain to get to but has to be done.

how easy are the plugs to get to? i had a little look earlier but couldn't see them.

My experience is you do not need to drain coolant when pulling carbs, but YMMV.

There's a full shop manual posted in the knowledgbase section if you need tech reference material.

I only do it because the manual says to, I've never tried without draining. I figured the heater lines would just spill all over the damn place if I didn't. If you can expand on that, I'd really love to hear that I don't actually have to drain my coolant to pull the carbs without making a mess.

I use clamps (that can be found in most auto parts stores) on the two hoses going to the carbs to keep the fluid loss down to almost nil.

Clean the carbs first. There is no reason to drain the coolant, hardly anything will spill out of the heater lines - I just elevate them slightly.


My bike with TBR mufflers runs fine at constant throttle from about 2,500 rpm on up, with stock pilot jets. Check the choke fittings to see if they are broken, which may have one of your enricheners sticking in the on position.


Clean everything, get it as close to stock as possible, then worry about tinkering with pilot jets, etc. When I bought my bike, it would barely make it up the driveway before I cleaned the carbs, replaced the air filter, etc.


You might want to check inside the tank for crud, rust, etc. too so you don't immediately foul your cleaned carbs. Don't forget to synchronize them when you're done.

Before you start messing with your carbs, you might want to do some more diagnosis on the stumbling problems. The FactoryPro website has some good stuff:

CV Carb Tuning Procedures

ok so had a ride and focused on what the bike was doing.

when it warmed up it got worse and was worse at higher speed when holding the throttle at a set speed.

it seems to be worse past 4000rpm
in the spares i got all the standard jets which are in the packets the jet kit come in with the # on the packets so im guessing they are the jets that where fitted.

jets are
pilot: 48
main: 190

i have the standard sizes in the packets but reading the page cadbury64 linked it sounds like its running rich which ties in with pilot jets being bigger.

so should i start by turning the pilots in on both by 1/2 a turn and testing?
how hard are the mixture screws to get to on these? ideally id like to avoid going into the carbs if i can but forum says #48 arent a great idea.

You should start by following the low speed mixture screw tuning procedure, rather than arbitrarily adjusting them. Each bike is different based on many variables and there is no right setting.

A good place to start
https://www.superhawkforum.com/forum...l-screw-26718/

This says 1,800 RPM, some prefer something around 1,000 RPM because the effects are more noticeable. Also, make sure to reset the idle speed with the idle speed screw after you adjust your first carb and move on to the second.

Sounds like you are very very rich. Stock is 175/178.

Read this, follow it and you will get real close.
https://www.superhawkforum.com/forum...-set-up-24769/

took a look, fuel mixture screws look a pain to get to..

went out for a ride got back and my partner had melted her shoe on my renegade carbon exhaust but just the left side, checked them and the right side i can hold without burning myself but the left i can touch for maybe 1-2 seconds before it burns, its a hell of a lot hotter than the right exhaust.

what does this mean?

also how easy are the plugs to remove to check? do i have to strip half the bike?

The hot can needs repacking.

Plugs are easy with the right socket. Front can be done without removing anything.

ok took plugs out, front was a bit black rear was fine.

took the carbs out as i couldnt get to the fuel mixture screws..

they where turned out 2 1/4 turns.
checked the jets..

front pilot 48
front main 190

rear pilot 48
rear main 190

i have renegade high rise cans and i have oem filter + k&n filter..

whats the best move from here?
put the 45 pilots in both?
or go back to standard jets with the cans i have and hope it works?

The only way to find out is to try it.

Part of the joys of owning a VTR .

I'm running stock mains in mine, with 45 pilots. I tried a lot of adjusting and couldn't get the 48s to run smooth, so i went back to the 45s. (The opinion on 48s is mixed, so best to try it for yourself and for your own opinion)

Here is what i have:
With 45 pilots:
Front fuel screw 2-1/4 turn out
Rear fuel screw 2-1/2 turn out
I saw the tach needle "hang" at 2000rpm when i blipped the throttle (it hunt when on its way back to idle) so I added 1/2 turn out to each carb and it didn't seem to hang anymore.
(Turn out to richen. Turn in to lean.)

Most long time Superhawk owners tell me they adjust the mixture screws for cold weather, then back for hot weather, basically two adjustments per year...

Check with Jack Flash for adjustable mixture screws (and don't Loctite them or you won't be able to adjust them, don't ask me how I know...)

James

Go to stock filter, and mains.

stock filter stock mains an 48 pilot?

Yes as per the Carb setup link I posted.

great thanks, i wanted to get it as close to perfect first time if i could as i dont have a garage or anything so ill be outside in the cold stripping it then bringing it inside.

Have you cleaned the carbs? Remove all jets, clean with carb cleaner, blow out with air (don't damage the diaphragms or hit them with carb cleaner)?


If they have been cleaned, then get your jetting closer to stock - it's too rich on top, almost guaranteed.


Fuel screws primarily affect idle
Pilots primarily affect idle to about 1/4 throttle
Needle position and taper about 1/4 throttle to 3/4 throttle
Mains about 1/2 throttle and up


So, does it idle?
What happens when you hit the throttle? will it pick up, or fall on its face?
Can you hit the throttle at low rpm and have it go, but high rpm it dies? Will it pull high rpm at all (if it won't you could have clogged jets from sitting)


To make things more confusing, they all overlap and affect each other a little.


Your main jets are way too rich at 190's, which makes sense with the stumble at 4,000 rpm and up. 45 pilot or 48 pilot will have some, but relatively little affect above 4,000 rpm.


Save your time with the carb setup link - if you have 45 pilots and roughly 180 mains, you will be much, much closer than you are now. Don't get me wrong, read it, but there is pages of information in there that can be a distraction, some good, some bad.


Unfortunately if you have aftermarket needles, getting them on the right clip setting is something else for you to battle with, and probably having the greatest affect on the 4,000 rpm range.


More exhaust flows through the left can than the right - the left can will always be hotter. Re-packing them if they are aftermarket cans is a good idea, like spokes says.


To sum it up:


Clean the carbs
Set them close to stock - 45 pilots, 178 or 180 mains, if aftermarket needles - middle clip for starters
Synch them (also primarily affects idle)


Run it and see. If you haven't cleaned them first, all bets are off.

And put an OEM air filter in...

When was the K&N last properly cleaned and reoiled?