Technical Discussion Topics related to Technical Issues

low speed right turn stumble

Old 08-26-2011, 08:38 AM
  #1  
Junior Member
Squid
Thread Starter
 
Join Date: Jul 2011
Location: nor cal
Posts: 21
chp_hates_me is on a distinguished road
low speed right turn stumble

i have the same problem as this guy. it always happens when going down a long steep hill off the throttle, then going into a hard right turn at less than 3k rpm.


https://www.superhawkforum.com/forum...stumble-17677/


i have been thru the carbs twice, sync'd them, cleaned them, TPS, new OE air cleaner,adjusted fuel screws with the idle drop method from the manual....all the obvious things. this just started happening recently, so it makes me thing something is worn, something has changed. i have been working on this thing for almost 1800 miles now trying to diagnose this problem. i work on it one night, then the next night take it out for 100 mile hell ride. last night it never missed a beat until 75 miles into the ride, and then got a stumble from the downhill, right turn thing. i thought i had it fixed, i was so damn happy too, then i happened again.

my float needles do have a wear mark on them, although i would not call it damage. i'm really starting to think that the bowl gets too full b/c the needle does not seal quite well enough, and when i go into the turn the vent gets submersed in fuel and then it hiccups. do the needles seal faces have to be pristine? there does not appear to be an elevation change on the sealing surface of the needle, just a smoothed witness mark where it hits the seat.

other than this one issue the bike runs perfectly. i have stock jets, needles shimmed up 0.5 mm.
bike has 50k miles on it.

Last edited by chp_hates_me; 08-26-2011 at 09:45 AM.
chp_hates_me is offline  
Old 08-26-2011, 10:45 AM
  #2  
Banned
MotoGP
 
Join Date: Aug 2007
Location: Lake View Terrace, CA
Posts: 5,942
8541Hawk will become famous soon enough
Do the float bowl vent lines still cross between the carbs? If so remove them from the carb stays and route them so they just point straight down.
8541Hawk is offline  
Old 08-26-2011, 10:57 AM
  #3  
Junior Member
Squid
Thread Starter
 
Join Date: Jul 2011
Location: nor cal
Posts: 21
chp_hates_me is on a distinguished road
so i would pivot the air fitting in the carb and point them down, probably make the hoses shorter too, or just get rid of the hose?

i will do this, but can you tell why that works? there is still 1 atmosphere of pressure at the end of the hose. does some of the fuel leak out of the vent and stop of the tube for a short time, and this mod lets the fuel fall out instead of becoming trapped in the horizontal section of vent pipe.
chp_hates_me is offline  
Old 08-26-2011, 11:07 AM
  #4  
Banned
MotoGP
 
Join Date: Aug 2007
Location: Lake View Terrace, CA
Posts: 5,942
8541Hawk will become famous soon enough
Well it's from a service bulletin that was released in '98 and generally only effects the earlier bikes but what is happening is the hole through the carb stay is a touch undersized.

What this does is very slightly pinch the vent line. So what happens is when you are going down hill, on the brakes, the rear carb pukes a bit of fuel into the front carb and you end up running on one cylinder until it clears out.

The bulletin stated to just remove the vent lines from the carb stays (where they cross each other) and just point them down instead of going through the stay. You can cut them down or whatever you want.

Sounds pretty simple but it really does work....
8541Hawk is offline  
Old 08-26-2011, 11:26 AM
  #5  
Junior Member
Squid
Thread Starter
 
Join Date: Jul 2011
Location: nor cal
Posts: 21
chp_hates_me is on a distinguished road
my vents are not linked together so i don't think one overflowing vent would allow fuel into the other carb's vent.

but they do travel horizontally them make a 90 bend and then into the holes in the carb stay.


any chance you could tell where to find that service bulletin? i would like to see some pics. when i first bought this cali model bike back in 99 i immediately removed all the PAIR and carbon can junk. so i have no idea what the float bowl vent hose routing for a 49 state model looks like.

yes mine is a very early model, it has SN# 43, yes the 43rd chicken ever produced

damn i hope this works, sure is a simple fix.
BIG thanks for the advice.

Last edited by chp_hates_me; 08-26-2011 at 11:49 AM.
chp_hates_me is offline  
Old 08-26-2011, 11:32 AM
  #6  
Banned
MotoGP
 
Join Date: Aug 2007
Location: Lake View Terrace, CA
Posts: 5,942
8541Hawk will become famous soon enough
The vent lies are not hooked together...... it comes from the throat of the rear carb, up the long stack and into the short stack......

No I have no link or pics, just a good memory.....lol and all the bikes (49 state or not) have the lines routed the same way. It was fixed in the later models, so it is only on the earlier bikes that you need to do this.
8541Hawk is offline  
Old 08-26-2011, 12:34 PM
  #7  
Banned
MotoGP
 
Join Date: Aug 2007
Location: Lake View Terrace, CA
Posts: 5,942
8541Hawk will become famous soon enough
Well not sure what part of NoCal you are located at.... it is kind of a big place..... but if you are near the Bay Area you could always bring it by and I can figure it out for you if you still have problems after you reroute the vent lines.....
8541Hawk is offline  
Old 08-26-2011, 12:49 PM
  #8  
Junior Member
Squid
Thread Starter
 
Join Date: Jul 2011
Location: nor cal
Posts: 21
chp_hates_me is on a distinguished road
i'm not too far from you, i'm in the santa cruz mountains. my guess is you do some riding around here.

ever go to alice's for breakfast?
chp_hates_me is offline  
Old 08-26-2011, 02:05 PM
  #9  
Member
Squid
 
Join Date: Sep 2009
Location: estonia,Tallinn
Posts: 42
franz125 is on a distinguished road
franz125 is offline  
Old 08-26-2011, 02:11 PM
  #10  
Banned
MotoGP
 
Join Date: Aug 2007
Location: Lake View Terrace, CA
Posts: 5,942
8541Hawk will become famous soon enough
low speed right turn stumble-stumbleafterbraking.jpg

Though the one I saw had you reroute both lines......
8541Hawk is offline  
Old 08-26-2011, 02:16 PM
  #11  
Banned
MotoGP
 
Join Date: Aug 2007
Location: Lake View Terrace, CA
Posts: 5,942
8541Hawk will become famous soon enough
Originally Posted by chp_hates_me View Post
i'm not too far from you, i'm in the santa cruz mountains. my guess is you do some riding around here.

ever go to alice's for breakfast?
Haven't been there in a while. When I lived in La Honda I was there all the time. Though things have gotten pretty bad over there on the weekends with all the squids and the popo they bring with them.

So I tend to spend more time on Mines\Mt Ham anymore when I do get a chance to go for a ride.
8541Hawk is offline  
Old 08-26-2011, 04:32 PM
  #12  
Junior Member
Squid
Thread Starter
 
Join Date: Jul 2011
Location: nor cal
Posts: 21
chp_hates_me is on a distinguished road
oh yeah, lots of squids and chp, hence on weekends i only go out at 6 am, do 100 miles or so, and am back home by 10 am. weekend evenings are great though. i railed down hwy 9 last night about 7, had the whole road to myself, my own personal track it seemed. i think i made from 35 to BC in 15 mins, damn it was fun.

planning to do hamilton/mines very soon, haven't been up there in a few months......how is the road? last time i was up there quit a bit of sand and gravel going up hamilton, mines was wonderful as always. love that road, never crowded and always a challenge.
chp_hates_me is offline  
Old 08-27-2011, 03:59 PM
  #13  
Banned
MotoGP
 
Join Date: Aug 2007
Location: Lake View Terrace, CA
Posts: 5,942
8541Hawk will become famous soon enough
Well I haven't had a chance to just go out and ride for around 1 1\2 months now but maybe in the next couple of weeks. I'll let you know if and when I'll be out there as there are a couple of other members asking about that ride also....
8541Hawk is offline  
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
jonymo
Modifications - Performance
13
08-02-2010 06:53 AM
seb421
General Discussion
30
06-29-2009 10:32 AM
oahu hawk
Technical Discussion
13
03-02-2009 07:33 PM
luv2insanity
Technical Discussion
11
08-31-2008 08:05 AM
Red_Liner740
Technical Discussion
2
07-20-2008 12:51 AM


Thread Tools
Search this Thread
Quick Reply: low speed right turn stumble


Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.