# Bogs under heavy acceleration



## InvalidID (Feb 18, 2011)

Ok fellas, same bike I was talking about in the points post. (Thanks for the help there guys)

I've got everything put together again, carbs cleaned, timing is spot on, yadda yadda.... But it's still running rich and if you really crack the throttle it'll bog out. If you crack it and hold it wide open it'll stall. It's clearly running a bit rich now, could this be the stalling problem too? Could it be a leaking vacuum somewhere keeping the timing from advancing fast enough?


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## bikehealer1 (Oct 8, 2009)

1. does it have a regular petcock or a vacuum activated one? 
2. how many turns out are the fuel/air mixture screws? 
3. did you pull the plugs and see which cylinders are running rich? 
4. will it pull through the flat spot? at what r.p.m. does it "bog"? 
5 . what size pilots and mains? 
6. stock airbox or pod filters?
7. how much fuel is in each float bowl? 

vacuum does not control the timing advance on this bike. it has a mechanical advancer that the points cam is mounted on.


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## InvalidID (Feb 18, 2011)

Vacuum petcock. I've even tried running it on prime to see if there is much of a difference. I'm honestly not sure if there is much of a difference, and if so it's not enough to mean a whole lot.

The metering screws are out about 2 3/4 turns. 

All of the plugs look a but carbon-ish, but number 4 is the cleanest.

Once it's warmed up it'll pull through the flat spot and run right up to red. You just gotta go easy on it, can't just crack it open. From idle if I crack it hard it'll die.

Pilots and mains are stock. I don't know what size, but I do know everything on the bike is as it was from Suzuki.

Right now there are no filters on it. I intend to put pods on it though as the box is ugly as sin.

I'm not sure how much fuel is in each bowl, how do I check that? I know it's not over flowing at least as there's no fuel leaking out of the vacuum port on the bottom of the bowl.


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## Bearfootfarm (Jul 13, 2006)

Are the spark plugs new?
If not, buy a set of NGK's


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## Steve in PA (Nov 25, 2011)

Motorcycle talk! Yes!!!

Did you put a jet kit on? If you didn't, find the instructions for a stage 3 jet kit. There are different settings for each phase of throttle (idle/half/wot). The setting for each of them is distinctive and a trade off with carbs. You can get it to run great at WOT, but will sacrifice some idle/half to get it for example.

It's bee quite a while since I did a jet kit, but going from memory I would guess it has something to do with the metering rods.

You did sync the carbs, right? Doing anything Carb related on a multicarb engine is next to impossible if the carbs aren't in sync. Also, you mentioned pods. Some engines just never run correctly with them. I had a Katana that hated pod filters.

Edit. I found a set of instructions http://www.dynojet.com/pdf/3321.pdf. My guess would be that you need to move the clip up one notch.


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## simi-steading (Sep 27, 2012)

InvalidID said:


> Right now there are no filters on it. I intend to put pods on it though as the box is ugly as sin.


You need to adjust the carbs with the air filters on it you plan to run.. If you change out the filters from stock, more than likely you will have to rejet the carbs.. you also need to sync them... You can get a gauge to help you do that.. 

I've rejetted a whole lot of bikes... It's a very fine balancing act trying to get the low circuit and high circuit to play well together... It's the transition between the two that will throw you, and create a problem like you are seeing... 

Sounds like you may be running too rich on the idle circuit...


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## bikehealer1 (Oct 8, 2009)

Ok.
Did you balance, or synchronize , the carbs? If the slides are not all opening at the same time then it will run poorly. 
Are you saying you have no airbox installed now? The airbox serves an important part in controlling airflow. Without it you have too much air entering the carb and not enough fuel being drawn up the needle jet to compensate.For this you will need to rejet- Steve in PA is right, a stage 3 is what you need. If you have the box installed with air filter, then remove each slide needle and move the clip on the needle down 2 slots(towards the pointed end ). this will raise the needle up, making fuel come out of the needle jet quicker. Bump up the main jets by about 2 sizes (they run in 5's { i.e. 165,170,175 } You may have to have the carbs off quite a few times. 
On the petcock- make sure fuel is not being sucked out of the nipple where the vacuum line hooks in. I have had quite a few leaking diaphragms lately that cause a richness issue. 
Checking fuel amounts in the bowl- drain each bowl into a container ( usually I put a hose on the nipple at the bottom of the bowl and drain into a 2.25 ounce shot measure glass.) Optimal amount of fuel is 1.5 ounces per bowl.
Plugs- ideally should be lightly brown to darker, not black. Number 4 being the cleanest means it may be perfect or too lean. Pictures are wonderful. 

Ive been doing this for a while, and the best thing I can say is make small changes at a time. Mechanical slide carbs require a smooth opening of the throttle, not the quick twist most people think.


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## InvalidID (Feb 18, 2011)

I bench synced the carbs but don't have the gauge to do a proper sync. I figure if I get it close enough I can have someone with the gauge fine tune it. These carbs were fairly easy to bench sync though as they have no butterfly or anything. I know that's not going to account for value wear and such though.

I'm going to put pods on it, so I think I'll wait to make anymore changes until they are delivered. I hope I don't have to rejet... If I'm lucky maybe the pods with be restrictive enough to straighten things out?... IF I'm running too rich on the idle circuit already though, restricting the airflow might not solve my problem eh?


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## foxtrapper (Dec 23, 2003)

Don't know what bike this is, but a couple of points.

Virtually all motorcycles bog if you snap the throttles open from idle. There is no accelerator pump circuit on most, and you must roll the throttle open instead. 

Needle height in the piston is set with a c-clip that holds the needle in place. Normally, oem postion is the center slot. Owners frequently enrichen the mixture by relocating this c-clip. This often causes bogging problems.

Lack of sync can cause bog problems, and does cause lurching and popping. Lack of synch makes tuning the bike all but impossible. 

Lack of air filters can make tuning the carburetors quite entertaining. Air filters are part of the setup.

Lack of oem air filters can make tuning the bike quite entertaining. Particularly Suzuki bikes. Suzuki bikes are very sensitive to air filter changes. Frequently causing the engine to bog and bang and other non-fast things.


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## InvalidID (Feb 18, 2011)

Funny you should mention suzuki... It's a 79 GS850


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## bikehealer1 (Oct 8, 2009)

how do you know you are running rich at idle? put in a set of clean plugs. crank and run without cracking the throttle. idle only. pull the plugs. what do they look like on the outer edge of the plug?


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## InvalidID (Feb 18, 2011)

bikehealer1 said:


> how do you know you are running rich at idle? put in a set of clean plugs. crank and run without cracking the throttle. idle only. pull the plugs. what do they look like on the outer edge of the plug?


 I think it's running rich at idle mainly due to the smell... I'll try the plug trick this evening thanks.


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