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View Full Version : Need Help! Carb/Jet ?


Brettstl
16th March 2012, 18:52
I have a 1998 883 hugger. The person i bought the bike from installed a 1200 kit on the bike, and also has drag pipes with no baffles. I put a velocity stack intake on the bike this weekend. I rode the bike which seemed fine when your giving it throttle but when you are at a constant speed it almost feels like the engine is cutting in and out. ( and after reading through this forum and talking to the hd dealer i bought a slow 45 jet and a 180 main jet) which i installed the next day because i figured i was not getting the fuel i needed....when i took the carb off i found the owner before me had a 48 slow jet and a 160 main jet installed...I put the 45 and 180 jet in and rode it again and the same thing is happening except i believe it feels a little better but def not ridable for long ....my question is what jet size should i have with this setup so my bike is back to normal...also one small note, when i put the jets in i also installed the kit from dkcustoms that relocates the coil...do you think moving the wires around could be causing this issue i am having. i dont believe the spark plug wires have been ever changed and the bike has 15,000 miles on it. Thank you.

rocketmangb
16th March 2012, 18:57
Welcome Aboard Brett !

Lets check the idle mix screw first OK ?

Brettstl
16th March 2012, 19:01
Welcome Aboard Brett !

Lets check the idle mix screw first OK ?

thank you!


it is at 4 turns out right now. i had it at 2 out first and it was backfiring through the carb.

rocketmangb
16th March 2012, 19:10
4 turns is waaaay out !

Lets check for an intake leak next !

Brettstl
16th March 2012, 22:51
4 turns is waaaay out !

Lets check for an intake leak next !

i will check for air leaks tonight. do you think the jet size could be causing the problem? The bike idle and revs up fine.

Don Burton
17th March 2012, 18:11
Here's something that Maru posted recently which may give you some ideas. http://xlforum.net/vbportal/forums/showpost.php?p=3840149&postcount=22

Brettstl
17th March 2012, 18:41
Here's something that Maru posted recently which may give you some ideas. http://xlforum.net/vbportal/forums/showpost.php?p=3840149&postcount=22



very good watch, but the problem happened after i installed the velocity stack. i rode for probably 3,000 miles with the drag pipes with no problem. The problem happens at constant rpm and almost feels like the bike jumps back and forth. you can def tell that the bike is cutting in and out.

rocketmangb
17th March 2012, 18:48
Check the bowl vent on the carb !
Make sure no part of the stack is obstructing the vent
The vent is on the face of the carb at 10 o clock between 2 bolt holes

maru
17th March 2012, 22:07
Can you post a photo of the velocity stack so i can see it?

Brettstl
18th March 2012, 15:32
Can you post a photo of the velocity stack so i can see it?

http://i1050.photobucket.com/albums/s413/Brettstl/IMAG0103.jpg
http://i1050.photobucket.com/albums/s413/Brettstl/IMAG0102.jpg
http://i1050.photobucket.com/albums/s413/Brettstl/IMAG0101.jpg

merc
18th March 2012, 15:37
what do your plugs look like?

Brettstl
18th March 2012, 15:42
what do your plugs look like?

plugs are a little white. I guess its running a bit lean?

rocketmangb
18th March 2012, 16:43
need you to pull the stack and check the bowl vent

Brettstl
18th March 2012, 19:20
need you to pull the stack and check the bowl vent


i will pull it soon and and check the vent and post more pics. do you mean the face of the carb there is a little cut out in the metal? If it would of got blocked by a new gasket would it cause a problem?

rocketmangb
18th March 2012, 19:23
There is a hole in the face of the carb @ about 10 oclock with no threads
That is the bowl vent

I have seen gaskets and stacks block that vent or restrict it

A carb will not work with out a vent.

Brettstl
18th March 2012, 19:26
There is a hole in the face of the carb @ about 10 oclock with no threads
That is the bowl vent

I have seen gaskets and stacks block that vent or restrict it

A carb will not work with out a vent.


gotcha i will check that out asap. thanks.

rocketmangb
18th March 2012, 19:28
Also make sure that stack aint sucking the Blue out of your Levi's !

Brettstl
18th March 2012, 21:23
rocketmangb is this the hole for the carb vent?
http://i1050.photobucket.com/albums/s413/Brettstl/conversion2copy.jpg

rocketmangb
18th March 2012, 21:37
Thats the one !

Brettstl
18th March 2012, 21:40
Thats the one !

ok well damn...i had a bolt in that hole. im a idiot. do you think that is what could be causing the problem then?

rocketmangb
18th March 2012, 21:45
Shit !

Bolts go at 2-5-9 !

wedge
18th March 2012, 21:48
ok well damn...i had a bolt in that hole. im a idiot. do you think that is what could be causing the problem then?
Certainly possible. How did you get a bolt in there with no threads? Careful that any bolts are not going to get sucked in, or you will have bigger problems than this surge that you have been having.

Then, it would be good if you read up in the carb/efi sticky section on how to set the mixture screw using the idle drop method. You should get it set to ear and feel rather than just putting it in different places to see what happens.

Brettstl
18th March 2012, 21:56
Certainly possible. How did you get a bolt in there with no threads? Careful that any bolts are not going to get sucked in, or you will have bigger problems than this surge that you have been having.

Then, it would be good if you read up in the carb/efi sticky section on how to set the mixture screw using the idle drop method. You should get it set to ear and feel rather than just putting it in different places to see what happens.



thanks guys im going to go take the screw out now and take it for a ride to see if that was the problem. ill keep you posted.

rocketmangb
18th March 2012, 22:23
Sounds like a plan !

wedge
18th March 2012, 23:05
Sounds like a plan !
Been an hour, so that's a good sign since he ain't back yet.

Brettstl
19th March 2012, 00:31
Been an hour, so that's a good sign since he ain't back yet.

haha yes. took the bolt out and now the bike is running good again.( had to take a little ride):clap I appreciate all the help guys....once i get some baffles in the exhaust and get my air/fuel mixture fine tuned hopefully the bike will be back to its former glory!

rocketmangb
19th March 2012, 01:48
Go figure !

Dem vents are tricky !

wedge
19th March 2012, 18:30
Go figure !

Dem vents are tricky !
Yeah, now we need to shove a potato-e up the exhaust and see what that does... :doh:D

rejeanprimeau
19th March 2012, 18:54
Is the potato going to have my bike run leaner or richer?

wedge
19th March 2012, 20:03
Is the potato going to have my bike run leaner or richer?
Not sure, but add a steak and it will be well fed... :D

Brettstl
27th March 2012, 12:49
hey guys maybe you can help me with another problem if you could. my bike runs great now since i unblocked the carb vent:doh...but now the exhaust will backfire at times its always when im just cruising at any speed at steady throttle. For an example if im on the highway it will pop out the exhaust and the bike feels like it misses somewhat for that second. it does not do it all the time, i rode for 6 hours sunday and it prob only did it 20 times...my question is do you think this is happening because i need different jets?

spiteboy
27th March 2012, 14:31
Having read through this thread I kept wondering about the velocity stack and the white plugs. In my experience; popping at steady throttle is a sign of a very lean mixture. I believe the velocity stack should allow a ton of air to be sucked into the pump, but your choice of jets seem rather standard for most applications with improved intake and exhaust. How do your plugs look now?

Something of note, I had a massive exhaust leak at the head that created the same symptom once upon a time. I suppose I would not rule out a leak leaning out the mixture if it is truly occuring at all speeds.

wedge
27th March 2012, 17:24
hey guys maybe you can help me with another problem if you could. my bike runs great now since i unblocked the carb vent:doh...but now the exhaust will backfire at times its always when im just cruising at any speed at steady throttle. For an example if im on the highway it will pop out the exhaust and the bike feels like it misses somewhat for that second. it does not do it all the time, i rode for 6 hours sunday and it prob only did it 20 times...my question is do you think this is happening because i need different jets?
Do you feel any surging, or just the pop and hesitation?

I would test the mixture by riding for a while at steady throttle where you feel the issue, then kill the engine with the switch on the bars as you pull the clutch in, and let it coast to a stop. Then pull the plugs and get a good reading. If you need help with that, look at "Plug Reading 101" in the sticky's (carb/efi section). Make sure you have some oil to oil the plug threads with when you do this, because it's especially necessary working on hot threads so you don't seize the threads.

spiteboy mentions a header pipe gasket leak, and he is right there too, so look for that as well. You can look for exhaust leaks by squirting a bit of oil in the jugs when the plugs are out and watching for smoke to come out around the head pipe when you fire it back up. You can also hear head pipe leaks with a stethescope if you listen around the flange.

It could also be an ignition/timing issue, so there is a lot to look at, just work one step at a time, testing in between until you find the culprit.

Brettstl
27th March 2012, 22:58
I would say it is more like a hesitation when the pop occurs. (kinda feels like a tap of the brake for a split second)...I got new pipes (with baffles) and are going to be installing them in a few days. I will check the gaskets to make sure there is no leaks then. I am hoping that the baffles will help out a bit with trying to get the mixture and jetting correct. I guess if the problem still occurs I will have to look into the timing and ignition. Also yes the plugs are still white last time I checked after riding.

wedge
28th March 2012, 03:41
I would say it is more like a hesitation when the pop occurs. (kinda feels like a tap of the brake for a split second)...I got new pipes (with baffles) and are going to be installing them in a few days. I will check the gaskets to make sure there is no leaks then. I am hoping that the baffles will help out a bit with trying to get the mixture and jetting correct. I guess if the problem still occurs I will have to look into the timing and ignition. Also yes the plugs are still white last time I checked after riding.
The plugs being white doesn't tell you much, except that the heat range is correct (white porcelain that is). Beyond that as far as determining if it is lean or rich, you need to read up on that plug reading 101 and learn where to look, and what to look for. It's easier to send you to that thread than repeat it here.