Re- jetting my carb-- questions.

[Brandon Whitmore]

I'm in the process of re- jetting my bike and have some questions.

I'm using a JD jet kit. All of the smog stuff has been removed from the bike-- do I need to modify anything from JD's instructions?

I took the carb. all the way off of the bike because I wanted to clean it up. I was worried about sand being in it, and need to clean the air boot between the filter and carb.

There was sand in the carb at the area where the carb meets the air boot (filter side of carb). I cleaned this area of the carb and still need to clean the air boot.

While I have the carb torn apart, is there anything I should do beyond the JD instructions since it's already apart?

My main question is this: While taking the needle jet out I had the slide and jet fall completely out of the carb (oops). The slide detached itself from the needle jet assembly. Does anyone have any pictures of how the slide should look when re- installed (based on youtube vid's I've got it right)? I've re- installed it so that the letter "M" (I think) on the slide is visible, and so that there is a hole near the bottom of the slide. Also, the slide does not completely seal when the throttle is disengaged-- is this the correct position?


The bike was running very poorly/ lean which is why I put in the jet kit. The settings prior to installing the kit were.
NEEDLE: 2nd from top.
MAIN JET: 185
PILOT JET: 52
LEAK JET: None
O-RING ON PUMP TIMING SCREW: None

New settings: (I'll be running 0-4000 feet for now)

RED NEEDLE AT POSITION 5
MAIN JET 180
PILOT JET 45
LEAK JET: DONE
THICK O- RING: DONE

Oh yeah. I removed the pump timing screw to install the O- ring. How many turns in does it go back in when re- installed? I now realize I never had to pull the screw to put the o- ring on, but it's been cold (teens) all day and I think my brain was frozen at the time.

Thanks in advance.

 

[Brandon Whitmore]

I found this on Thumper Talk:
http://www.thumperfaq.com/ap.htm

I think the part labeled "Accelerator Pump Timing Adjustment" covers my question in regards to adjustment of the screw, but it's late and I may just be in over my head.

It looks like if I stick a small rod in at the gap of the slide and then adjust the screw, the screw should suddenly hit resistance when set correctly? Hopefully I'm not sounding like an idiot. I'll re- read the site listed above tomorrow-- it may be more clear after some sleep. Not that I get much sleep with an infant to watch over at night.

 

[rabskyline]

i just left pumper stock ..about 2mm of thread showing out and put "o" ring over it and it pulls pump harder when you crank harder instead of letting spring push it at a certain rate... works a treat ! maybe too much of a treat though as it had plenty of grunt as it was ! lol..

 

[Brandon Whitmore]

Thank you sir.

 

[Brandon Whitmore]

I'm hoping for a little help from a jetting guru.

I got the bike back together and it fired right up with the choke "on". It seems to run good with the choke on, but runs poorly and backfires with the choke "off".

Questions:

1)Could this be a timing issue? Maybe something to do with the timing chain. I just got the bike, so I don't know it's history.

2)I am set exactly to JD's specs for my bike and altitude. Does the JD jet kit typically require tweaking for a bike to run right?

3)Since the bike runs well with the choke on, could I have an air leak somewhere? If so, what's the best way to find out where, etc? Can I throw a bunch of soap on the engine and watch for bubbling like I would for a nat. gas leak?

Any other pointers or input would be appreciated.

 

[jmetteer]

I am not a jetting guru, but here is my 2 pesos... To me it sounds like your bike is lean.

Not sure if it is a timing issue, how did it run before the JD kit?


I have only done a couple JD kits in 4 strokes. Mine ran perfect per the instructions. My friends WR250F Yamaha ran like crap, but he had the stock exhaust restrictor and air box snorkel removed. His bike needed the blue needle installed, then it ran much much better.

If your bike has an exhaust it could throw off the baseline JD kit.

Does it idle without the choke on? If it doesn't you may have too small of a pilot.

Here is a good way to check your pilot circuit.


If it idles fine without the choke on but pops when you rev it up without the choke on it is probably the needle. If you have the red needle in try the blue one in the same position. If you have the blue needle in, move the clip down one and try that.

To check for air leaks, carefully spray something flammable (carb clean/starter fluid/wd40) around the carb area with it running. If it revs up you have an air leak.

Later,

 

[Brandon Whitmore]

Hi Jake,

Thanks for the reply.

Not sure if it is a timing issue, how did it run before the JD kit?

It ran lean-- plug was white. The bike shop that checked it out said that the jetting was all over the place. It did run much better before the JD kit. It only popped on decel, and had the white plug.

Does it idle without the choke on? If it doesn't you may have too small of a pilot.

Based on memory, it idled at very low RPM's, but did idle OK with the screw turned up more than typical.

If it idles fine without the choke on but pops when you rev it up without the choke on it is probably the needle. If you have the red needle in try the blue one in the same position. If you have the blue needle in, move the clip down one and try that.

I've got the red, so I'll try the blue.

Thanks for the great info/ advice. One I play with it more I'll report back............

 

[ctslacker]

keep me posted. ive got a 06 te510 that i just put a jd kit in and pulled all the smog crap also. it ran pretty crappy before . would pop stall with throttle. no power and backfiring on deceleration . preliminary run was great but still have backfire and popping on deceleration low rpm now. but air temp is much cooler now. so jetting may still be off, btw this bike pulls like a two stroke . i love it and street legal its almost like cheating. jetting is a trial and error just don't run lean. jd has great cust service call them and they may be able to help.

ctslacker

 

[Brandon Whitmore]

Hi ctslacker,

I'll keep everyone posted as soon as I can get to it. I'm playing Mr. Mom with my infant on days off of work, so I'm having trouble getting out to the shop.

I was on JD's website last night reading their FAQ's. With their info., and Jake's help, I should have plenty to go on for now.

Stay tuned.

 

[Brandon Whitmore]

Today is the day to play with my carb.

What I've found so far.

1)Bike idles with choke on or off.

2)There's no air leaks I can find -- I sprayed a healthy dose of WD on everything.

3)When the choke is on and I give it some gas, there is a slight decel type pop when I let off-- sounds lean even with the choke on.

4)When the choke is off it pops and backfires when I give it gas.

5)If I give the throttle a quick twist, it misses and does nothing. I've got to slowly twist the throttle to get the RPM's up.

That's it for now.

 

[Brandon Whitmore]

New Settings:

JD Jet kit.

Blue needle in clip position 4 as per manuf. recommendations.

185 main jet. Everything else is still the same for now.

Bike sounds much better, but I'm not there yet.

Concerns

Bike is still a little off/ misses when I quickly crack the throttle, so I need to find out the issue here.

Upper RPM range misses, doesn't sound like it fully revs, and there is a pop when I let off of the throttle

 

[tirebiter]

Did you block off any holes or left over open smog tubes connected to the intake manifold or carb after you removed the smog equipment? If you didn't, that could be why your running lean.

 

[Brandon Whitmore]

Hi tirebiter,


All of the smog stuff was already removed when I purchased the bike. I need to check out the manual and try to figure out where all of the stuff was connected.

Something else to check out-- thank you.

 

[pvduke]

I'm in the process of re- jetting my bike and have some questions.

I'm using a JD jet kit. All of the smog stuff has been removed from the bike-- do I need to modify anything from JD's instructions?

I took the carb. all the way off of the bike because I wanted to clean it up. I was worried about sand being in it, and need to clean the air boot between the filter and carb.

There was sand in the carb at the area where the carb meets the air boot (filter side of carb). I cleaned this area of the carb and still need to clean the air boot.

While I have the carb torn apart, is there anything I should do beyond the JD instructions since it's already apart?

My main question is this: While taking the needle jet out I had the slide and jet fall completely out of the carb (oops). The slide detached itself from the needle jet assembly. Does anyone have any pictures of how the slide should look when re- installed (based on youtube vid's I've got it right)? I've re- installed it so that the letter "M" (I think) on the slide is visible, and so that there is a hole near the bottom of the slide. Also, the slide does not completely seal when the throttle is disengaged-- is this the correct position?
.

Doood...ya need to address the SAND issues fist.
Why was there sand in your intake?

Carb will only go back together one way. The right way.

Hard bog = lean / Burble = rich (in a lot of cases)

Identify which circuit needs attention, after, you start from the idle circuit and go up from there. And, after you verify there's no leaks anywhere. Use GUMOUT or some motor-start fluid to look for leaks, not WD40.

Crash course on carb workings:

Idle - 1/4 TO = screw/PJ
1/4 - 1/2 TO = PJ/needle
1/2 - 3/4 TO = needle/main
Etc.

The AP only covers the hole ya make when ya whack the throttle open and has diddly to do with how your bike meters fuel for a given TO.

Get mechanical issues sorted first. Then, if the unit has 100% compression and all is good then address driveability issues.

 

[Brandon Whitmore]

Doood...ya need to address the SAND issues fist.
Why was there sand in your intake?

Hi pvduke,

I've changed my oil, cleaned out the carb, and cleaned the air box.

The sand was most likely in my intake due to the fact that the previous owner didn't seat the filter properly.

I called the guy who inspected the bike for me and he doesn't seem to be concerned. He told me that the engine was strong and he doesn't think there's anything to worry about.

One good thing is that I have the jetting set much better than it was, but it still needs some tweaking. When the bike is cold, it'll fire but quickly die with the choke off. With the choke on, it fires right up with no problems.

Crash course on carb workings:

Idle - 1/4 TO = screw/PJ
1/4 - 1/2 TO = PJ/needle
1/2 - 3/4 TO = needle/main

Thanks. I've found some really good websites that have helped tremendously-- gotta love the internet.

Get mechanical issues sorted first. Then, if the unit has 100% compression and all is good then address driveability issues.

I don't think I have any mechanical issues (just jetting), at least I hope not. My bike inspector said compression was fine and a compression test wasn't needed.

Per his inspection, I needed a jet kit, a new chain, both new sprockets, wheel bearing replacement and a fork seal replacement. The fork seals were weeping slightly upon inspection. I've done everything he said needed to be done besides the fork seals which aren't urgent.

I do have one question......

The other day the engine was hot and when I tried to kick start the bike it sort of backfired/ coughed, but did not fire on that kick-- what causes that?

Thanks.

 

[pvduke]

I do have one question......

The other day the engine was hot and when I tried to kick start the bike it sort of backfired/ coughed, but did not fire on that kick-- what causes that?

Thanks.

Make sure your air box/boot junction is not leaking and your filter is in top condition. There should be no grit in the carb- EVER.

You may be opening the throttle, this causes kick-back. Put your hand on the bar when kicking. I sometimes yank the gas by accident after a stall and I'm in a hurry. *POP!*...up through the kick-starter.
If it fires back through the ex pipe like a shotgun it may be something else.

 

[Brandon Whitmore]

Thanks pvduke.

It popped through the exhaust I believe. After doing more reading, I have a feeling it's due to rich jetting.

I appreciate the help/ info.

 

[Brandon Whitmore]

Today I installed my finger adjustable fuel screw. One thing I noticed is there didn't appear to be a washer on the screw I pulled out-- the washer I am talking about is the one that goes between the spring and carb.

Is a washer typically installed at this location on a stock fuel screw?

If so, I'll pull it back off and see if the original washer stuck up in there.

I'm hoping that the washer is stuck up there somewhere and that's preventing proper adjustment. If not, I think I'll have to get a different sized pilot jet.

Thanks in advance for any answers. It's going to bug me until I know the answer, and I'm not in the position to take it apart for a couple of days.

 

[RLW]

Today I installed my finger adjustable fuel screw. One thing I noticed is there didn't appear to be a washer on the screw I pulled out-- the washer I am talking about is the one that goes between the spring and carb.

Is a washer typically installed at this location on a stock fuel screw?

If so, I'll pull it back off and see if the original washer stuck up in there.

Yes, there is suppose to be a washer between spring and o-ring.......I would definitely look and make sure it's not stuck up in there.

Just curious, which extended fuel screw did you go with?

 

[pvduke]

Tilt carb, place rag under it, pull screw VERY CAREFULLY and look for washer.