Bogging at 3500 RPM & at a loss where to go next

[Roemy24]

With your guys help I've made progress but not riding yet. I got the carbs cleaned....very clean. Like Pacman suggested I got the low speed passages in the carbs taken care of and that took care of the bogging I encountered as I gave it throttle.

Now I can get it up to 3500 but then it bogs. If I give it choke (no throttle) I can get 4000-4500. Where to go next?

'80 850L - New intake o-rings, new carb kits (stock), airbox is definitely sealed, K&N air filter recharged. It idles and warms up very nice. Backfires some on startup until it settles down after minute. I can't find any air leaks.

Suggestions? Worked on this thing all last summer and still haven't gave up hope but would like to take one ride this year :-\\\

 

[Roemy24]

Also float heights are in range and float (tested.)

 

[Dave8338]

Valves adjusted and carb sync done?

 

[Roemy24]

Yes and yes

 

[tkent02]

Throttle slides lifting correctly?
Holes in diaphragms?
Spark advance operating smoothly?

Sounds like too lean when it is bogging, if the choke helps.

 

[Roemy24]

Throttle slides seem to be correct and slide nicely.
No holes in diaphragms that I could find, used a light to shine back through.
Spark advance operating smoothly, how would do I go about checking that?

I'll play around with the choke when it is bogging down and report my find this evening.

How high should I be able to rev with just the choke?

 

[rustybronco]

Spark advance operating smoothly, how would do I go about checking that?

With a timing light.


Were the installed jet(s) the correct size(s) as the originals?

 

[Dave8338]

One more thought: When I rebuild my carbs, the jet needles that came with the kits were tapered wrong (more blunt) than the originals and as a result, are still in the drawer. :-k

 

[salty_monk]

Make sure the holes in throttle slides are stock size & haven't been enlarged by someone else....

Definitely check your needles. I would use Mikuni only. Did you renew the clamps for the carb boots & airbox? The K&N does flow more air than stock so that won't be helping. If the 850 is like the 1000G box the side plates have to be sealed properly to the box otherwise air can get in the side & bypass the filter.

 

[Roemy24]

When I put the new kits in, I stayed with the original needles because I noticed the difference. All the jets where correct as the originals. To tell you the truth, two clamps just broke last night on me. I think I'm going to order new intake and airbox boots to help elminate some problems as well as clamps. As for the K&N, I know I have the sides sealed very well. Would I need to turn the air screws to compensate for it?

 

[Roemy24]

So some more evalution. No leaks around the intake boots. No leaks around the airbox boots however I get a slight rise (500rpm) or so when I spray the top of the side covers, both sides. Yes that is a problem but I can't see it would cause all this problem. I'll take care of that in the days to come.

I can rev it to 4500 and pull the choke and it will race to 5-6K then backfire a few times and practically die out. Is it time to pull the carbs and clean for the fourth time? The only issue I had this last time was the needle valve seat filter screen/filter kept falling off. The new ones don't stay as well as the originals. I would attempt to clean the originals but have seemed to miss place one and missing a screen from another. I did verify that they were on the best I could when I reassembled.

Also I was only able to get it to around 4K before so I backed out the air screws to almost three turns each. It did seem so run a little better and did get my RPM's a little higher.

 

[rustybronco]

partially cover the air snorkel opening with duct tape and see if it runs better, or temporarily duct tape around the chrome end caps and see if it runs better.

your air box has the rubber style end seals correct ?(I don't have a gl to look at)
if it does, glue the rubber seals to the air box, lightly put some grease on the air box seals and check for a complete impression of the side air box seals to end covers.

 

[salty_monk]

Yes, those leaks could be causing your problems.

You also might want to think of getting a spacer stack (load of washers) from Radio shack & going up one spacer (stack of washers same height as the plastic washer - take one & put it below the clip allowing more of the needle to "poke through" at the top.
This is like raising the needles half a notch (if it had notches like the old days) & it might help a bit.

 

[Guest]

If the carbs are clean and the airbox tight you may be looking at a weak ignition.

 

[Roemy24]

I'll make sure the airbox is sealed next time I work on it. It does have the rubber seals. I think I'll use some weatherstripping on the inside of the chrome covers.

I will keep the washers in mind. What I don't understand is why I would need to do this when it was new and stock it didn't need it from the factory. Now it is just old and stock but needs it?

Is there any documents on the site that show how to test the ignition? New at this but will try anything once!

Thank you for all the replies so far! Keep them coming.

 

[salty_monk]

I had a weak ignition causing the same thing at 6k rpm but it didn't improve any when I messed with the carbs.

The Clymer's manual lists tests for the trigger & the ignitor - they are fairly simple to do but you do have to tape some wires to a AA battery & use it to test one of them from memory... (unless you have a better multimeter than me..). It's most likely to be the box not the trigger. Cure is to fit a DYNA S ($120 at Z1)

Your bike isn't stock - you have a free flowing filter - aftermarket Jets (from KL no doubt.. you might want to think about getting real Mikuni ones if so or even getting the 2.5 stage higher set to compensate for the K&N) & leaking airbox!

What exhaust are you running? Stock? Is it well sealed too?