what to do now...

[ski3747270]

Hoping shawn and mark can help on this one...

96 with cobra pipes. KN and a jet kit (type..?) came on the bike. 8xxx miles.

Had it for about 5 months now, and running against my buddy's 99 with kerker 4-1, it seemed to run pretty close,but he always had me top end.
He or I could never get my bike to do a burnout. He said that was strange. When he followed me, he always smelled gas from my bike.

The right lower cobra pipe (when viewed from the rear) always had the smell of fuel and was always wet inside the pipe with unburnt fuel. I could live with this, and determined that cylinder was rich.

Today, after about 10 minutes of normal city riding, I jumped on the highway. 10-15 minutes later, that pipe (or at least that side) started to pop intermittently. I chalked it up to bad gas. several minutes later, the popping or backfiring was almost steady. This was in 5th gear at about 80-90 mph. It had never done this before. Ever.

Embarrassed enough, I turned around and headed back home and jumped online.

I read about how to do the 'shotgun' fix, and decided to face the monster and take off the carbs. I got them off okay, and realized 3 of the 4 idle screws were pretty stripped, and while I was checking how many turns they were in/out, some were so stipped, I only got 3 or 4 turns until they wouldnt move anymore. ****.

I was able to take out PA 1 and PA2, the main needles (the big long ones), shoot some cleaner in, hit it with compressed air, and I put it all back together with no parts left over thank god.

I can also tell you that the needles were set on the 3rd notch.

She started rough, taking about 2 minutes to fire (I attribute that to the bowls being dry), and idles okay.

I have yet to ride her.

Did I troubleshoot appropriately, and is there a fix for stripped idle air screws? (hoping sean morley will hook me up if there is)

You guys seem to be the jedi masters for these carbs, and I only jumped into the carbs after reading all your input to other posts. Please let me know what other info you might need to diagnose my initial problem.

I will post tomorrow when I ride the highway.

Whoever put in this jet kit stripped bunches of screws, and the 30 dollar craftsman screw-out set i bought did nothing but strip even more. Thanks Bob Villa.

Chris

 

[ski3747270]

I forgot something. I get about 75-80 miles before the fuel light comes on. This is daily driving, not hammer down all the time.

Chris

 

[shawn kloker]

Did you write down what the jet sizes were?Cobras need to be leaner than stock(152.5). You also need to figure out what jet kit it is.Dynojet or Factory pro.They use different size jets with the same number on them.Factory pro uses Mikuni jets, Dynojet invented their own.

Did you inspect the diaphrams real good.Hold them up to a light to see if any comes through.

The stripped air/fuel mixture screws will have to come out.I had one once and had to drill it out.I wrapped black tape around the bit to use as a guide.It was a real bitch but finally came out with out any damage.

 

[ski3747270]

Roger, the diaphragms looked good. I dont understand what caused this backfiring suddenly though.

I'll get the jet info when I get back from the road.

Thanks for the reply.
Chris

 

[ski3747270]

Backfiring/popping stopped altogether.

I did notice, however, that starting from a dead stop in 1st, the engine stumbles a bit, and I even stalled it at a stoplight. Once running in 1st gear, the engine hesitates very slightly, but then kicks in like a vboost once more throttle is applied.

It will take some getting used to, but the bike runs I'd say at about 98 percent.

All in all, I learned alot about the carbs, types of jets, how to clean them, and general nomenclature of parts. Did have a heck of a time putting the fuel line back on....

Thanks
Chris

 

[maxcruiser]

My experience is when it comes to carb problems, or poor performance due to carbs not turned properly, etc... it's usually time for a complete tune up.

The first place to start when you realize the bike is not running correctly is to pull the plugs and have a look at them. Every manual has a page with pictures of spark plugs showing rich condition etc...

If your plugs are showing anything other than a normal condition, than it's time to tune up the bike.

Start with the simpliest things first, check the idle screws settings (should be approx 2.5 turns out) do a carb sync, one or more carbs out of sync can appear as a rich or lean condition. Next check the CV boots for cracks. Run some carb cleaner through the fuel tank or better clean the pilot jets manually, etc....

If the simple checks don't fix the problem, than the carb bank needs to come out for more intensive look. (this also needs to be done if unsure of jetting set up, etc...) I won't into how to do this, but i've added a link which further areas of carburation, etc... Once on main page click tips than scroll down to carburation (lots of good info)

If you take carb bank off - one important area to check is the intake and vboost assembly rubber boots( especially on an older bike). Take them off and and bend them to see for cracks. This could have been the problem in the first place and causes a lean condition especially when engine is hot and without realizing it you try compensate with other adjustments.

It's almost impossible to diagnose a carb problem when reading a short thread and than give the magic solution to your problem.

Every carb based bike (engine) requires tuning and unless you have endless amounts of $$$ you will need to learn the carb basics to keep bike running strong.

Good luck

 

[maxcruiser]

Ooops, here's the link

Let's try this again:ummm:

The link is; www.awol.co.za/vmax_tech_tips.htm

Sorry about that!

You can also do a seach under "CV carb basics" and should fing some good info

 

[shawn kloker]

Backfiring/popping stopped altogether.

I did notice, however, that starting from a dead stop in 1st, the engine stumbles a bit, and I even stalled it at a stoplight. Once running in 1st gear, the engine hesitates very slightly, but then kicks in like a vboost once more throttle is applied.

It will take some getting used to, but the bike runs I'd say at about 98 percent.

All in all, I learned alot about the carbs, types of jets, how to clean them, and general nomenclature of parts. Did have a heck of a time putting the fuel line back on....

Thanks
Chris

I'd say you need to adjust those stripped out A/f mixture screws.