Sputtering/Bouncing slide at off idle RPMS HELP!!!

[Troll]

I have that same chart somewhere. I needed it when I reworked the carbs and air box on my W

[kfoster]

Interesting - on the face of it, that jet would be leaner than stock, but that may not really be the case.  If the jet is a Dynojet replacement, it is a bit fatter than the stock Keihen jet. Here is a comparison chart. The manufacturers use different numbering systems!

Width------Keihin # -- DynoJet # -- Mikuni #
0.0350---- 92.5--------- 92----------- 86.3
0.0360---- 95----------- 94----------- 88.1
0.0370---- 97.5--------- 96----------- 90.0
0.0380---- 100---------- 98----------- 91.9
0.0390---- 102.5------- 100---------- 93.8
0.0400---- 105--------- 102---------- 95.6
0.0410---- 107.5------- 104---------- 97.5
0.0420---- 110--------- 106---------- 99.4
0.0430---- 112.5------- 108--------- 101.3
0.0440---- 115--------- 110--------- 103.1
0.0450---- 117.5------- 112--------- 105.0
0.0460---- 120--------- 114--------- 106.9
0.0470---- 122.5------- 116--------- 108.8
0.0480---- 125--------- 118--------- 110.6
0.0490---- 127.5------- 120--------- 112.5
0.0500---- 130--------- 122--------- 114.4
0.0510---- 132.5------- 124--------- 116.3
0.0520---- 135--------- 126--------- 118.1
0.0530---- 137.5------- 128--------- 120.0
0.0540---- 140--------- 130--------- 121.9
0.0550---- 142.5------- 132--------- 123.8
0.0560---- 145--------- 134--------- 125.6
0.0570---- 147.5------- 136--------- 127.5
0.0580---- 150--------- 138--------- 129.4
0.0590---- 152.5------- 140--------- 131.3
0.0600---- 155--------- 142--------- 133.1
0.0610---- 157.5------- 144--------- 135.0
0.0620---- 160--------- 146--------- 136.9
0.0630---- 162.5------- 148--------- 138.8
0.0640---- 165--------- 150--------- 140.6
0.0650---- 167.5------- 152--------- 142.5
0.0660---- 170--------- 154--------- 144.4
0.0670---- 172.5------- 156--------- 146.3
0.0680---- 175--------- 158--------- 148.1
0.0690---- 177.5------- 160--------- 150.0
0.0700---- 180--------- 162--------- 151.9
0.0710---- 182.5------- 164--------- 153.8
0.0720---- 185--------- 166--------- 155.6
0.0730---- 187.5------- 168--------- 157.5
0.0740---- 190--------- 170--------- 159.4
0.0750---- 192.5------- 172--------- 161.3
0.0760---- 195--------- 174--------- 163.1
0.0770---- 197.5------- 176--------- 165.0
0.0780---- 200--------- 178--------- 166.9
0.0790---- 202.5------- 180--------- 168.8
0.0800---- 205--------- 182--------- 170.6
0.0810---- 207.5------- 184--------- 172.5
0.0820---- 210--------- 186--------- 174.4
0.0830---- 212.5------- 188--------- 176.3
0.0840---- 215--------- 190--------- 178.1
0.0850---- 217.5------- 192--------- 180.0
0.0860---- 220--------- 194--------- 181.9
0.0870---- 222.5------- 196--------- 183.7
0.0880---- 225--------- 198--------- 185.6
0.0890---- 227.5------- 200--------- 187.5

Based only on your description, I would still try lowering the needle a bit to see if there is improvement. This is frustrating, but when you get it right, you will be very happy with the bike!

[Jake Morales]

So the carb has a 132 size main jet and 48 size pilot jet. Could this be causing trouble? I've seen that it's supposed to have a 135 main jet

[Jake Morales]

Gotcha, that might explain why it got a little better after I debaffled the muffler. I will try that next though. I plan on taking the carb off one more time and going through it thoroughly. I appreciate all the replies. I love the way this bike looks and feels and I want to get it to run right.

[kfoster]

This link is a good explanation of CV carb tuning. It is oriented more towards high rpm motors, but you will get the idea.

http://www.factorypro.com/tech_tuning_procedures/tuning_carbtune,cv,high_rpm_engines.html

[kfoster]

An adjustable e-clip and washers indicate that it is an aftermarket main jet needle. The stock needle is not adjustable. The Drifter 800 carb is identical to the four on my ZRX. It would be interesting to find out what size main jet he has in the thing. I bet it is not stock either. Most kits are designed to be used with less restrictive exhaust systems. To use it with a stock system you would need to lean it out from the settings with the kit.

It sounds like the previous owner had not figured out how to get it to transition from the pilot jet to the needle. Three turns out or so should be just fine with the pilot. Try putting the washers on top of the e-clip and lowering the needle just a bit. If you are getting black smoke, you are running rich. The needle may need to come up a bit more slowly. If it improves, move the needle down a notch and see if it gets better.

[Jake Morales]

Okay so it wasn't the EGR valve. It was the air valve switch. I decided I'm going to put it back on and connect all the vacuum tubes so I can eliminate one problem at a time. I texted the guy and he said he only replaced the gasket, float needle  and the diaphragm in the carb. This is such a discouraging time ):

[Jake Morales]

Okay so I downloaded the pdf manual for the dynojet kit for my bike. I remember when I took the carb apart that the needle did have an e clip on it and two small washers. So does that mean that the dynojet kit was put in with the needle that comes with it? I honestly think this guy before me has no clue about what's going on in the bike haha.  if the dynojet kit is in the carb, is there anyway I can help the bike without removing the dynojet kit? I de baffled the muffler today (mostly) and it seemed to help with the black smoke. Certainly sounds less like a scooter now! But it still sputters at off idle. It seems like it is sputtering less but I can't tell.

[Troll]

Ok, so go to the Dynojet web site and download a copy of the installation manual for the jet kit they sell for your bike. It's a .PDF file. This will give you a bit more insight into that carb. Don't expect it to run perfectly until it's warmed up, the EPA fixed that for you. You said you removed or disconnected the EGR..What EGR? Motorcycles don't have EGR valves, that's a car thing (thank GOD!)

[Jake Morales]

Pilot is now open about 3 and a half turns and it runs a little better but still a bounce at low rpms. Took it for a test ride and it stalled twice while tryin to take off. The guy before me said that he rebuilt the carbs so I'm assuming he drilled out the plug then and he said it was all set back to factory settings. It's just confusing me and I want to be able to commute before registering it

[Troll]

It shouldn't run at all with the pilot screw bottomed out. Pilot should be open about 3 turns.Idle should be around 900-1000 rpm. It's not unusual to have a little bounce in the slide at low rpm, but how much is too much. Is the enrichment plunger going all the way back in to seat? These are pretty simple carbs. I wonder if someone hasn't tried to install a jet kit, since the pilot screw is sealed by a tamper proof plug.

[Jake Morales]

I did check the vacuum hose. I actually disconnected it from the petcock and plugged it and use prime as the on position to run the bike

[kfoster]

Did you check the vacuum hose to the petcock from the carb for cracks and leaks. That is a possible cause of this condition.

[CDNRatMan]

   Welcome, and some of the real mechanic lads will be along some time today to help you out. Once you get this fixed you will be really happy with your bike.

[Jake Morales]

I just traded a 2003 Buell Xb9r for a Vulcan 800 Drifter of the same year with 21,000 less miles but it has some issues. When I started it up, it was shooting out black smoke and smelled rich and it sputtered at low RPMs. I took off the air filter and can see the slide and butterfly valve bouncing just off idle. I removed the EGR valve and plugged up the hoses. I ended up screwing the pilot screw all the way in and it still shot out a little smoke but it didnt smell rich, but the slide still bounced up and down at the lower RPMs. If i pull the throttle and modulate the slide with my finger, it runs smooth through the RPMs. I removed the carb and checked the diaphragm and floats and needle and everything seems fine. I'm completely stumped. Could the exhaust baffle be clogged and causing too much back pressure? The bike is completely stock. No aftermarket filter and no aftermarket pipes. As soon as it gets passed the low RPMs it runs good. Somebody please help! I love this bike. I NEVER see these around anywhere and I want it to run right!