1982 GS450L bogging on acceleration

[dackcommabig]

Having an issue with my 82 GS450L. It idles like a champ, but when I give it some gas in gear, it bogs like crazy. It has Mikuni BS34 carbs on it and I have done all the normal tuning with the mixture screws. Carbs have been dipped and cleaned, but these carbs have a different jet setup than my Gs650g. It does have pods on it, and I doubt the jets have been upgraded from stock. I suspect the mains need to be bigger, but wanted to see if anyone had any other ideas before I spend any money. It is -2 degrees here in Iowa anyway, so I have some time to figure it out!

Thanks

 

[Guest]

Let me highlight the important parts:

Having an issue with my 82 GS450L. It idles like a champ, but when I give it some gas in gear, it bogs like crazy. It has Mikuni BS34 carbs on it and I have done all the normal tuning with the mixture screws. Carbs have been dipped and cleaned, but these carbs have a different jet setup than my Gs650g. It does have pods on it, and I doubt the jets have been upgraded from stock. I suspect the mains need to be bigger, but wanted to see if anyone had any other ideas before I spend any money. It is -2 degrees here in Iowa anyway, so I have some time to figure it out!

Thanks

If you have pods, you WILL have to change the jets. Which jets you need will depend on which pods you have installed.

Did you install the pods or did you get the bike that way? If you installed the pods, hopefully you changed them for a reason more important than "looks". If the airbox was mangled or missing, yes, pods might be a reasonable alternative, but simply changing to pods for "looks" is a practice that needs to be rewarded by a good flogging.

 

[dackcommabig]

Thank you for the info, I figured that was it. No, the pods were not installed for visual purposes. When I got the bike it had no intake or air filters at all, so flogging averted in this case! Should I do the pilot jets as well, and how much of a size increase am I looking at?

 

[steve murdoch]

This site has an excellent search feature.
An old thread but some info to at least get you going in the right direction.
http://www.thegsresources.com/_forum/archive/index.php/t-160455.html

Stock exhaust? Numbers may change depending on the system.

 

[sam000lee]

What type of pods do you have? What about the exhaust? There are a few people on here that have put pods on their GS450's that can give you some advice but we need a little more information.

 

[dem3500]

if its stock jetting and it bogs with pods then its mostly a lean bog which is not good at all. if it was me id go two sized up on the main and work your way back down if you needed.

 

[Lorenzo]

if its stock jetting and it bogs with pods then its mostly a lean bog which is not good at all. if it was me id go two sized up on the main and work your way back down if you needed.

Why the mains? They are supposed to affect carburation, from 2/3 throttle openings all the way to top, while it seems the problem is from 1/3 up, pilot jet territory.

dackcommabig can you post a pic of your sparks, and also positively check the size of your pilots?

 

[gs45082]

I have an 82 model as well, a TXZ. Mine had pods and straight pipes when I bought it (still quieter than a lot of HD's lol), and it took 135 mains to get it running right. I came across a stock exhaust, it continued to run great after I installed it so I just left the 135s in. I tried some 120's (the only others I had on hand) and it fell right on it's face at WOT, although it might still be OK with 130's if I were to get them.

Having an issue with my 82 GS450L. It idles like a champ, but when I give it some gas in gear, it bogs like crazy. It has Mikuni BS34 carbs on it and I have done all the normal tuning with the mixture screws. Carbs have been dipped and cleaned, but these carbs have a different jet setup than my Gs650g. It does have pods on it, and I doubt the jets have been upgraded from stock. I suspect the mains need to be bigger, but wanted to see if anyone had any other ideas before I spend any money. It is -2 degrees here in Iowa anyway, so I have some time to figure it out!

Thanks

Don't buy a jet kit, go on jetsrus and order the specific jets you need. They get 3 or 4 bucks apiece for stock equivalent jets plus 7 or 8 per order to ship. In your shoes I'd order 130's and 135's, you won't be out much more than $20.

 

[TxGSrider]

If its idling ok and you have between 3/4 and 3 turns on your idle mixture screws, then your pilots are probably pretty close. If its bogging at less than about 1/2 throttle then try moving the clip down a notch and see if it gets better... if you don't have adjustable needles, then go to the hardware store and pick up some small washers that fit under the needle (and seat properly inside the throttle valve) and put one or 2 under the clip and see if it helps.

After that, then you can mess with the main jets.

 

[Steve]

Actually, installing washers under the clip does nothing except increase the spring pressure that holds the needle in place. :-k

What you need to do is find those small washers (the assorted washer pack at Radio Shack has them, if you still have a Radio Shack in your area) and stack them next to the nylon spacer that is ABOVE the clip. You may find that it takes four or five washers to equal the thickness of the spacer. Remove about half of the washers, put them in place ABOVE the clip, in place of the nylon spacer.

The reason you don't usually have to increase the size of the pilot jets is simple. The size of the jet is based on the airflow that it needs to feed. When you remove the stock airbox (which is rather restrictve at full throttle) or change the exhaust (which is not all that restrictive), you allow more air to flow at full throttle. When you are at idle or part-throttle operation, it's the throttle that is your restriction, not the airbox, so nothing has really changed in air flow capability. Stock pilot jets work well until you go with a MAJOR over-bore kit, and then you might need to go up ONE size. In the meantime, determine how far out the pilot screws are turned. They should probably be in the range of 2 1/4 to 2 3/4 turns out from lightly seated. If they are not there, try it, that might fix your low-speed stumble. If they ARE already there, try another 1/8 to 1/4 turn to see if that helps.

.

 

[TxGSrider]

Actually, installing washers under the clip does nothing except increase the spring pressure that holds the needle in place. :-k

What you need to do is find those small washers (the assorted washer pack at Radio Shack has them, if you still have a Radio Shack in your area) and stack them next to the nylon spacer that is ABOVE the clip. You may find that it takes four or five washers to equal the thickness of the spacer. Remove about half of the washers, put them in place ABOVE the clip, in place of the nylon spacer.

The reason you don't usually have to increase the size of the pilot jets is simple. The size of the jet is based on the airflow that it needs to feed. When you remove the stock airbox (which is rather restrictve at full throttle) or change the exhaust (which is not all that restrictive), you allow more air to flow at full throttle. When you are at idle or part-throttle operation, it's the throttle that is your restriction, not the airbox, so nothing has really changed in air flow capability. Stock pilot jets work well until you go with a MAJOR over-bore kit, and then you might need to go up ONE size. In the meantime, determine how far out the pilot screws are turned. They should probably be in the range of 2 1/4 to 2 3/4 turns out from lightly seated. If they are not there, try it, that might fix your low-speed stumble. If they ARE already there, try another 1/8 to 1/4 turn to see if that helps.

.

Hey Steve, I know you're an expert on these (Im not being sarcastic at all), but I don't see how "installing washers under the clip does nothing except increase the spring pressure that holds the needle in place". I mean, yes I understand that it would apply a little more pressure the spring, but it should also raise the needle in relation to the throttle valve and make the mixture richer as it would sit higher on the valve. http://www.bing.com/images/search?q...6e155f9de70d41bed0ba11c63be5594co0&ajaxhist=0
Im talking about placing them just under "92037" just above "43028".

 

[Steve]

Take a good look at the setup there. The spring pushes the needle (and clip) UP, until it can't go any higher. The nylon spacer determines how far down from the top the clip will sit. It basically does not move at all during operation, it is stuck at the top of its travel all the time. Installing anything under the clip (between the spring and the clip) only adds tension to the spring, pushing it tighter against the retainer that keeps it from going anywhere. You can add old shock springs, it just won't go any higher.

Now, if you put in a thinner spacer, the needle will sit a bit higher, giving you the richer mixture you are looking for.

Back about 1980 or so, one of the magazines was trying to make the new EPA-spec bikes more user-friendly. Everybody was complaining of poor starting, long warm-up times and generally poor running due to the lean mixtures that were necessary to meet EPA specs. The magazine (I don't remember which one) wanted to keep it simple and cheap, and started by choosing what they thought was the worst example at the time. They chose a '79 GS425. They removed the plugs over the pilot screws and turned the screws out about 1/2 turn, then pulled the needles out of the slides and swapped the nylon spacer for the thin metal washer. They put the metal washer above the clip and the nylon spacer under the clip. That raised the needle about 2mm, which is a bit extreme, but it worked very well for their bike.

Of course, they had to caution everybody that this was illegal to do, the EPA police might knock on their door and all that stuff, but their objective was to show how little it took, and how inexpensive it was, to take a bike that ran horribly and get it to run MUCH better.

.

 

[TxGSrider]

Take a good look at the setup there. The spring pushes the needle (and clip) UP, until it can't go any higher. The nylon spacer determines how far down from the top the clip will sit. It basically does not move at all during operation, it is stuck at the top of its travel all the time. Installing anything under the clip (between the spring and the clip) only adds tension to the spring, pushing it tighter against the retainer that keeps it from going anywhere. You can add old shock springs, it just won't go any higher.

Now, if you put in a thinner spacer, the needle will sit a bit higher, giving you the richer mixture you are looking for.

Back about 1980 or so, one of the magazines was trying to make the new EPA-spec bikes more user-friendly. Everybody was complaining of poor starting, long warm-up times and generally poor running due to the lean mixtures that were necessary to meet EPA specs. The magazine (I don't remember which one) wanted to keep it simple and cheap, and started by choosing what they thought was the worst example at the time. They chose a '79 GS425. They removed the plugs over the pilot screws and turned the screws out about 1/2 turn, then pulled the needles out of the slides and swapped the nylon spacer for the thin metal washer. They put the metal washer above the clip and the nylon spacer under the clip. That raised the needle about 2mm, which is a bit extreme, but it worked very well for their bike.

Of course, they had to caution everybody that this was illegal to do, the EPA police might knock on their door and all that stuff, but their objective was to show how little it took, and how inexpensive it was, to take a bike that ran horribly and get it to run MUCH better.

.

So are you saying there's a small spring that is missing from this diagram that fits underneath the clip but above the throttle valve that holds the needle up?
FYI- I ask the questions not to doubt those of you that know allot more about motorcycles than me, but so I can learn.

 

[dem3500]

Why the mains? They are supposed to affect carburation, from 2/3 throttle openings all the way to top, while it seems the problem is from 1/3 up, pilot jet territory.

dackcommabig can you post a pic of your sparks, and also positively check the size of your pilots?

the op said when he gives it gas in gear. the main starts working just off idle, not at almost WOT. id almost say it starts at 1/4 or 1/3 throttle. at 2/3 throttle the needle is almost all the way out meaning the main has had an affect way before that.

 

[sam000lee]

Here's some reference pictures from when I was doing my 450. Like Steve said, get the Radioshack washers. You get a ton of them (a bunch are the wrong size) but the little bag is like $2.50 or something.

"Blowout" of the circlip, needle holder stay thing, stock spacer (orange thing), needle and clip (non adjustable), washer (to catch spring) and spring.

Height difference:

Original spacer:

Washers replaced:

 

[Lorenzo]

In case I got myself misunderstood, I wasn't referring to the pilot AIR screw but, to the jets inside the float chamber.
Following my line of reasoning, if the engine bogs at pickup, the pilots might be of too big a size.
Worth also investigating the jet needle, (after having cleared the pilots and the idle mixture screw).

 

[dem3500]

so if the needle rests on the clip than how does putting washers on top of the clip raise or lower the needle?

 

[sam000lee]

The top of the spacer/washers sits against the bottom of the retainer (held in a fixed height by the circlip) and is pushed against it by the spring. Lessening the height of the spacer (removing a washer) allows the spring to push the needle higher.

 

[Lorenzo]

It artificialliy alters the tapering of the jet needle

 

[TxGSrider]

The top of the spacer/washers sits against the bottom of the retainer (held in a fixed height by the circlip) and is pushed against it by the spring. Lessening the height of the spacer (removing a washer) allows the spring to push the needle higher.

BTW- Thank you for the pics. As I suspected, the online diagram didn't show that little spring underneath the clip. Now what Steve said is crystal clear.