Jump to content

  • Follow us:

  • Facebook
  • YouTube
  • Twitter
  • Google+
  • Instagram
  • RSS Feed
  • Google+





Photo
- - - - -

Strange jetting carb behavior?


  • Please sign in to reply

45 replies to this topic
  • Krannie McKranface
36,190 posts
Location: California
Garage View Garage

Posted October 10, 2016 - 06:29 PM


I'm dealing with a hanging idle problem right now - ended my ride pretty much right after I started today because it was dangerous in the woods. Came home, pulled the 45 pilot and put in a 48 thinking maybe a lean issue. Didn't get a chance to go back out, but in the garage, it still did it once. And when it hangs up, it hangs up at 6000 rpm, occassionally less, so that's not cool. A light blip will generally being it back down. Been intermittent since I had the carb off to clean in July. No air leaks that I can find and the slide is not hanging up visually with throttle movement. I'm guessing it's crappy fuel screw tuning on my part. I have zero bog, good All around power, and it starts perfectly cold or hot. Annoying. Why haven't I bought a 450FX yet...

 

Lot's of issues can contribute to hanging idle, usually it's not throttle/mechanical.

Here are the most common I know of:

 

- fuel screw lean

- fuel screw adjustment started with the idle way too high

- fuel screw oring torn or missing

- pilot is too small (45 is nearly 100% of the time the correct size)

- pilot jet is visually clean, but corroded inside - needs to be new

- pilot passage above jet has corrosion, leaning out the pilot. Must be soaked in solvent and reamed with wire or fishing line

- loose or cracked air boots

- slide plate seal is bad

- worn out slide bore; wheel grooves put the slide in the wrong place


Edited by Krannie McKranface, October 10, 2016 - 07:27 PM.


  • RockerYZWR
1,396 posts
Location: Florida
Garage View Garage

Posted October 13, 2016 - 02:57 PM


Lot's of issues can contribute to hanging idle, usually it's not throttle/mechanical.
Here are the most common I know of:

- fuel screw lean
- fuel screw adjustment started with the idle way too high
- fuel screw oring torn or missing
- pilot is too small (45 is nearly 100% of the time the correct size)
- pilot jet is visually clean, but corroded inside - needs to be new
- pilot passage above jet has corrosion, leaning out the pilot. Must be soaked in solvent and reamed with wire or fishing line
- loose or cracked air boots
- slide plate seal is bad
- worn out slide bore; wheel grooves put the slide in the wrong place

Fuel screw o-ring is missing - the larger one up by the spring. The little skinny one near the bottom is there. When I took the carb apart to clean it in July, it was not there at that time - I didn't realize one was supposed to be there at all. Angled a little mirror up into its hole with a bright light just now and it's not lodged up in there, either. So now where to find a viton o-ring that size locally... It would be awesome if this was the issue.

  • Krannie McKranface
36,190 posts
Location: California
Garage View Garage

Posted October 13, 2016 - 03:40 PM


There is only one oring on the fuel screw

  • RockerYZWR
1,396 posts
Location: Florida
Garage View Garage

Posted October 13, 2016 - 03:58 PM


Talking about the skinny little one on the left part of the needle there, probably not more than a dust seal. The one at the tip is missing.

tus_09_fue_mix_scr.jpg

  • Krannie McKranface
36,190 posts
Location: California
Garage View Garage

Posted October 13, 2016 - 04:06 PM


Talking about the skinny little one on the left part of the needle there, probably not more than a dust seal. The one at the tip is missing.

tus_09_fue_mix_scr.jpg

 

Those are washers, a spring, and an oring.

 

The bottom washer is optional.

 

BY THE WAY you should not use an alloy fuel screw. They break off insidet the carb, and if they aren't the kind that break, then they are tapered, which makes tuning a pain....

 

You want brass...

 

https://www.google.c...chrome&ie=UTF-8



  • Agazza

    TT Bronze Member

124 posts
Location: Sweden
Garage View Garage

Posted October 15, 2016 - 02:19 AM


The link is bad for me, I just put in a alloy one, but the carb is coming out again in a few months

  • RockerYZWR
1,396 posts
Location: Florida
Garage View Garage

Posted October 16, 2016 - 07:12 PM


Alright, I ordered the R&D remote fuel screw (brass), the Tokyomods AP spring (my linkage has been safety wired this whole time with no issues) and hot start nut, and the CRFs Only '08 CRF pump diaphragm kit, along with some shiny new Keihin main and pilot jets and a NCVQ needle (for the hell of it). I will reclean and inspect the carb in an extremely thorough fashion...hope this damn hanging idle will be gone after this and I hope it runs even stronger with the Tokyomods and CRFs Only pieces than it did before.

With the hot start nut, I inspected the stock plastic one and lubed the cable; it seemed to be a little slow on the return. Inspected for cracks, found none, and even teflon-taped the threads. Started it up...f-ing 5000-6000 rpm hanging idle still about every 3rd or 4th rev. Visually inspected throttle linkage while running and slide is definitely closing all the way. Hopefully I'll get all the parts this week.

  • Krannie McKranface
36,190 posts
Location: California
Garage View Garage

Posted October 16, 2016 - 08:01 PM


Alright, I ordered the R&D remote fuel screw (brass), the Tokyomods AP spring (my linkage has been safety wired this whole time with no issues) and hot start nut, and the CRFs Only '08 CRF pump diaphragm kit, along with some shiny new Keihin main and pilot jets and a NCVQ needle (for the hell of it). I will reclean and inspect the carb in an extremely thorough fashion...hope this damn hanging idle will be gone after this and I hope it runs even stronger with the Tokyomods and CRFs Only pieces than it did before.

With the hot start nut, I inspected the stock plastic one and lubed the cable; it seemed to be a little slow on the return. Inspected for cracks, found none, and even teflon-taped the threads. Started it up...f-ing 5000-6000 rpm hanging idle still about every 3rd or 4th rev. Visually inspected throttle linkage while running and slide is definitely closing all the way. Hopefully I'll get all the parts this week.

 

There is one other, very rare reason for hanging idle.....a contaminated/melting internal split-body gasket. Debris gets in the passages, or the seal actually partially covers some passages.

 

I am inspecting a carb this week for a haning idle I cannot get rid of with any of my own advice.....and I have seen it before in the past, from using automotive carb cleaners on the FCR carb....that can actually melt the seal if you are agressive enough with the cleaner...



  • RockerYZWR
1,396 posts
Location: Florida
Garage View Garage

Posted October 17, 2016 - 03:46 AM


There is one other, very rare reason for hanging idle.....a contaminated/melting internal split-body gasket. Debris gets in the passages, or the seal actually partially covers some passages.

I am inspecting a carb this week for a haning idle I cannot get rid of with any of my own advice.....and I have seen it before in the past, from using automotive carb cleaners on the FCR carb....that can actually melt the seal if you are agressive enough with the cleaner...

Just to be sure, we're talking this gasket here? Or float bowl gasket (which is the only one I would have had exposed)?
http://www.ebay.com/itm/272381659175
1476704472366.jpg
Any special tools or tricks required to get to that gasket?
Only places I used carb cleaner (Berryman's in this case) was in the accelerator pump passage after reaming it out with a little piece or wire, followed immediately by air, and other passages, but immediately followed by air as well. Didn't let anything soak in it at all. Thanks a lot for the help.

Edited by RockerYZWR, October 17, 2016 - 03:47 AM.


  • Krannie McKranface
36,190 posts
Location: California
Garage View Garage

Posted October 17, 2016 - 05:07 AM


That's the one



  • RockerYZWR
1,396 posts
Location: Florida
Garage View Garage

Posted October 17, 2016 - 05:38 AM


Thanks a lot.

  • jamesm113

    TT Bronze Member

172 posts
Location: California
Garage View Garage

Posted October 17, 2016 - 07:56 AM


Any special tools or tricks required to get to that gasket?
 

 

You need torx security bits to open up the mid-body.

 

JD Jetting has a little bit better prices on the gaskets:

https://www.jdjettin...2&cat=18&page=2

https://www.jdjettin...6&cat=18&page=2

 

They also have some good pictures of the mid body:

http://www.pbase.com.../image/75676614



  • RockerYZWR
1,396 posts
Location: Florida
Garage View Garage

Posted October 17, 2016 - 08:09 AM


You need torx security bits to open up the mid-body.

JD Jetting has a little bit better prices on the gaskets:
https://www.jdjettin...2&cat=18&page=2
https://www.jdjettin...6&cat=18&page=2

They also have some good pictures of the mid body:
http://www.pbase.com.../image/75676614

Hey, excellent - thanks very much for the help. I had the order in with CRFs Only for the Honda AP diaphragm, and just emailed them to see if they could add the midbody gasket before they ship it out (same price as JD). Only thing I'm not sure of is if I need that slide guide gasket. And are there two midbody gaskets? Many of the pictures I see show two in the same pic with slightly different designs.

  • jamesm113

    TT Bronze Member

172 posts
Location: California
Garage View Garage

Posted October 17, 2016 - 08:26 AM


I'm not sure.  I've only dove this deep on a buddies pre-2003 YZ carb.  He got a little overzealous with a routine cleaning and pulled the midbody. :banghead:   No-one had the correct mid-body gasket for those early carbs, so we had to cut one and use a bit of gasket maker and hope for the best.

 

But for $4 more, I'd say you might as well get the slide guide gasket.  It'd be better to have it and not need it than need it and not have it.

 

Also, for what it's worth, I wouldn't want to go this deep again unless it was a last resort.


Edited by jamesm113, October 17, 2016 - 08:26 AM.


  • RockerYZWR
1,396 posts
Location: Florida
Garage View Garage

Posted October 17, 2016 - 03:11 PM


Ended up stopping my midbody gasket order after talking with the nice people at JD Jetting and ordered a new slide plate seal. So hopefully all the parts will be in this week and Friday night will be carb rebuild night.

  • RockerYZWR
1,396 posts
Location: Florida
Garage View Garage

Posted October 21, 2016 - 09:07 PM


Welp, I found my problem ... At least I'm 99% sure it was my problem. While installing all the new, wonderful parts I bought for my carb, and specifically while replacing the needle, I found that the screw that holds the slide linkage to the throttle shaft was way loose. I had checked that the "slide was closing" with the engine running just by watching the throttle shaft close completely - I think the slide, especially with engine vacuum pulling against it, was hanging up independent of the shaft. So there we go, add that to the list of possibilities for a hanging idle - especially an irregular or intermittent hanging idle. Simple!

I still put in the following parts:
- New jets - 168 main/45 pilot
- NCVQ needle (on 4th clip)
- Honda CRF accelerator pump
- Tokyo Mods AP spring
- R&D Flex fuel screw
- New slide plate seal (old one was fine, now have spare)
- Tokyo Mods aluminum hotstart nut
- New drain and vent tubes (bright yellow, why not)

I didn't have any bog before, but I could kill the engine sometimes with a very quick throttle snap with no load. I noticed it does not do that now, just instant revs. Quick test ride down my street at 10:30 pm, shows no noticeable dead spots and very good power, although I didn't really get after it since I had flip flops on, it was dark, and I'm a responsible adult.

Loose slide linkage to throttle shaft screw!
  • Krannie McKranface and Agazza like this
  • Like This

  • Krannie McKranface
36,190 posts
Location: California
Garage View Garage

Posted October 22, 2016 - 05:55 AM


Welp, I found my problem ... At least I'm 99% sure it was my problem. While installing all the new, wonderful parts I bought for my carb, and specifically while replacing the needle, I found that the screw that holds the slide linkage to the throttle shaft was way loose. I had checked that the "slide was closing" with the engine running just by watching the throttle shaft close completely - I think the slide, especially with engine vacuum pulling against it, was hanging up independent of the shaft. So there we go, add that to the list of possibilities for a hanging idle - especially an irregular or intermittent hanging idle. Simple!

I still put in the following parts:
- New jets - 168 main/45 pilot
- NCVQ needle (on 4th clip)
- Honda CRF accelerator pump
- Tokyo Mods AP spring
- R&D Flex fuel screw
- New slide plate seal (old one was fine, now have spare)
- Tokyo Mods aluminum hotstart nut
- New drain and vent tubes (bright yellow, why not)

I didn't have any bog before, but I could kill the engine sometimes with a very quick throttle snap with no load. I noticed it does not do that now, just instant revs. Quick test ride down my street at 10:30 pm, shows no noticeable dead spots and very good power, although I didn't really get after it since I had flip flops on, it was dark, and I'm a responsible adult.

Loose slide linkage to throttle shaft screw!

 

You are lucky you did not suck that screw into the motor.....



  • RockerYZWR
1,396 posts
Location: Florida
Garage View Garage

Posted October 22, 2016 - 06:07 AM


Yeah, now that I think about it, next time the tank is off, I'll probably go back in and put a little Loctite on that one. Though I'm not sure if there's enough room for that screw to slip through, but it's definitely something that needs to be checked every 50 hours or something.

  • RockerYZWR
1,396 posts
Location: Florida
Garage View Garage

Posted October 22, 2016 - 01:20 PM


The bike ran flawlessly today! Noticeably stronger low- and mid-range - I'm a fan of the NCVQ needle. A buddy of mine commented that it even sounds different...I told him that's because I also put on some new grips.

Very happy with the WR right now!

  • Krannie McKranface
36,190 posts
Location: California
Garage View Garage

Posted October 22, 2016 - 02:21 PM


The bike ran flawlessly today! Noticeably stronger low- and mid-range - I'm a fan of the NCVQ needle. A buddy of mine commented that it even sounds different...I told him that's because I also put on some new grips.

Very happy with the WR right now!

 

It's the apump spring. Makes it livelier.






0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users

 
x

Join Our Community!

Even if you don't want to post, registered members get access to tools that make finding & following the good stuff easier.

The views and opinions expressed on this page are strictly those of the author, and have not been reviewed or approved by ThumperTalk.