Snap, crackle, pop... - Solved (I think) 08/04

[Xtracho]

The phat lady runs good...after about 2500 RPM. She stutters and backfires when I run at a steady 2500 RPM more or less. And also backfires when sitting at idle at a red light. I do know that I have an exhaust leak on the left side that I will remedy. And will also snug up the header bolts. Above that 2500 and she's running fine.

I replaced my carb set with a set I got from a member but I have not done the carb sync yet. And I'll pull the plugs and take a look at them. Carbs were torn down and cleaned real good before install. I'll also take a look at the vacuum plugs. I have an extra set from Red Eye.

Bike is Shiny Desmogged.

Just rode from home to Louisiana and back; getting about 23-25 mpg on the highway running at about 75-80 mph. Ran a bottle of Seafoam, a bottle of Techron, and a bottle of B-12 Chemtool on the trip.

Wanted to get some feedback on anything else I may troubleshoot. Thanks in advance!

[Jess Tolbirt]

sounds to me like you need to get the carbs synced..a compression check would determine if there is a problem with the valves and pistons..if all cyl. are close then i say carb sync.

[Xtracho]

Thanks Jess....valves adjusted about 5K miles ago when I did the rear end service. The backfire is just from the left side.

[Hoser]

My bike ran on 5 cylinders up to 2500 rpm, ran fine after that.  It had a broken carburetor spring.  replaced spring, ran fine. A really easy fix, might check it, just in case.  Hoser   

[Xtracho]

Thanks Hoser....just finished the carb sync. #2 & #6 were way out. #1 & #5 were just a little off. Seems to have cured the popping at idle anyhow. We'll see if it lasts. And I'll check that carb spring as well.

[Ricky-D]

23-25 mpg on the highway running at about 75-80 mph

That's terrible gas mileage.

Regardless-

***

[Xtracho]

23-25 mpg on the highway running at about 75-80 mph

That's terrible gas mileage.

Regardless-

***

I agree...with the Pingle petcock I was looking for a gas station at about 100 miles when normally it would have been around 125. This was my first long trip on the bike with that new Pingle installed. Hopefully the carb sync will help with the mileage as well. Like I said, the left bank #2 and #6 were way out of sync.

[Ricky-D]

The petcock should not have any influence on gas mileage.

And a carburetor synchronization has a very little to no affect upon

gas mileage.

Sounds to me like aftermarket stuff in the carburetors and maybe

other air pump bolt-ons.

***

[Xtracho]

No aftermarket in the carbs that I could see when I tore them down. Replaced intake runner gaskets and bowl gaskets. Floats and needle valves looked good as well. The mileage did improve somewhat the more I rode with the Seafoam, Techron, Chemtool fuel treatments. I'll check my desmog stuff to make sure there are no leaks. I did find a cracked vacuum plug on one of the runners when doing the sync. Will also pull plugs and take a good look at them. They have not been changed since I bought the bike. Maybe time to do that.

[Thunderbolt]

Did you change the small vacuum lines to the cut valves when you had them off and disassembled?  They are about 1 1/2" long.  They sometimes have small cracks that are not visible until you squeeze the ends.

[Xtracho]

Did you change the small vacuum lines to the cut valves when you had them off and disassembled?  They are about 1 1/2" long.  They sometimes have small cracks that are not visible until you squeeze the ends.

Did not and where are they located on the bike? I tried to get rid of as much vacuum crapola as I could when I desmogged.

[Jess from VA]

WAG (wild ass guess)... could your choke NOT be all the way off, thou seemingly off at the handlebar?

[Xtracho]

Thanks Jess....ANY input is appreciated. I'll check that as well. Pulled the plugs yesterday and they do look worn somewhat. Ordered a new set. At least the carb sync ended the popping at idle. I also ran her up to 2500 RPM's and there was no popping or backfire either. 2 of the 3 carbs on the left side were way out of sync. I'm going to take her out for a 50 mile ride or so and see what the gas mileage will be.

[Regis]

mine was doing that on the right side , turned out it was #3 cyl . and was the vacuum cap on the intake . its desmogged

[Thunderbolt]

The vacuum lines are on each carb on the left side, not looking at it right now but think it is left.  The easiest one to see is #5, the rear one on the right side.  You can change some of them without removing the carbs.

[Xtracho]

 :coolsmiley:OK...carb sync yesterday seems to have solved the popping on idle and up to 2500 RPM's. From that 2500 RPM's and up, when I hold throttle at a steady RPM, she still pops. Although not as loud it seems. The most noticeable is between 2500-3500 RPM's. So I suppose the slow jets can be ruled out at this point. I am going to go through all the desmog fittings and make sure they are good and tight and not sucking air. I also ordered a new set of NGK plugs. Maybe not a fix, but looking at the plugs as they sit, I feel good about replacing them.

Quote from Thunderbolt:

The vacuum lines are on each carb on the left side, not looking at it right now but think it is left.  The easiest one to see is #5, the rear one on the right side.  You can change some of them without removing the carbs.

Going to look at the schematic to see if I can figure what vacuum lines you are referring to. I thought I got rid of all the vacuum crapola to the intakes when I did the desmog. 

[Momz]

Did you plug the vacuum nipple on the air box?

[Xtracho]

Well silly ass me  ... while reinstalling the chrome pieces that cover the screws for the carb adjustments I found the 3 screws for each diaphragm cap were loose. I probably forgot to snug them down when I installed the V-stacks.  again. Some were a good 2-2.5 turns from being snugged on the left side. Tightened them up, took a short ride...and right back to popping at lower RPM's as well as the upper. My uneducated guess is that my carb sync is no longer any good since the diaphragm covers were not tightened as they should be. So...I'll do another carb sync tomorrow and see what I get.

Did you plug the vacuum nipple on the air box?

Momz I'm pretty certain I did. When I go over all the desmog fittings tomorrow I'll look at that as well. I'd really like to exhaust all options before deciding to pull the carbs again. But I will if I have to.

I really appreciate all you guys brainstorming possible solutions  , because my brainstorming usually amounts to nothing more than a drizzle.   

[Xtracho]

Pretty much at my wit's end with the popping and backfire from 2500 RPM's and up on the left side. Changed the plugs this morning on that side....no luck. So...I pulled the V-stacks and diaphragm covers and this is what I found under the cover for #5>>>



The spring was fractured and out of its place under that cover.

I have an extra set of carbs so I scavenged a spring from one of them. Installed it, fired the bike up and revved her to 2500, 3000, and 3500....no more popping, backfiring. Of course I'll need to take a test ride to make sure. But so far so good.  

[Jess from VA]

I suppose those are not interchangeable with these.   

[Xtracho]

LMAO Jess...I was gonna tear my Para 14-45 apart and find out!! Good one! 

[Jess from VA]

If memory serves, they (.45s) need to be 15-22lbs, depending on the load, length of barrel and the tension of the hammer spring.  Probably too stout and too wide.  I save all my old ones, I don't know why.

Probably no good for the kickstand either.  

[Xtracho]

LOL...yeah you're right....maybe from the Ruger SR22 I use for plinking.

[Hoser]

Thanks Hoser....just finished the carb sync. #2 & #6 were way out. #1 & #5 were just a little off. Seems to have cured the popping at idle anyhow. We'll see if it lasts. And I'll check that carb spring as well.

Aha, gotcha, The Hoser rules!   Glad you found it.  Hoser 

[Xtracho]

Thanks Hoser....just finished the carb sync. #2 & #6 were way out. #1 & #5 were just a little off. Seems to have cured the popping at idle anyhow. We'll see if it lasts. And I'll check that carb spring as well.

Aha, gotcha, The Hoser rules!   Glad you found it.  Hoser 

  Yup....the roost is ruled! Thanks again!