Backfire problem 1987 Venure XVZ13DT

[CptKirk]

I recently bought a 1987 XVZ13DT and started to clean it up. The boost sensor wasn't working so replaced it with a newer used one, it did help with the backfire problem to some degree but the bike still backfires .

 

The symptoms are that if you slowly come onto the throttle it will reach 4000 rpm then crap out badly.If you crank the throttle on it backfires really badly and will not pickup RPM.

 

Backfires through number 2 carb and the exhaust. The slides do not move much and just dance about at a partial opening when the backfiring starts.

 

Timing is okay, carbs are synched (checked them). Ignition coils and wires are good according to the manual, pickup coils are are okay (a least all the resistances match my other Venture which runs great). TheTDI is a newer one. Battery is new and fully charged. I checked the fuel pump pressure which is good. Grounds are cleaned up good. It starts up and idles but has a slght miss on idle. Comperssion is 170 accross all four cylinders.The carb slide diaphrams are visually good on all 4 as are the slides. Plugs are new but black an sooty as are the exh pipes.

 

So my thoughts are dirty carbs and a lean out a higher RPM as I have done all I can to the igintion system in terms of newer parts. Seems it will not transition to the high speed loop of the carbs. Hoping for some wisdom in how to fix the problem.

 

The bike was an ebay buy and is a real looker chrome wise but chrome don't get you home. I have redone the fork seals and bushings, new steering head bearings and progressive springs with superbrace. Newer rotors and brake pads. Have an 83 XVZ12TDK as well which has been a great ride I would take anywhere and have.

 

Any wisdom to confirm my thoughts or any ideas are surely welcome. This is a great site and have noticed some really great people willing to help keep these classic bikes on the road.

 

Sincere best wishes to you all.

 

[CptKirk]

I just opened the carb drains and had look at what the state of the contents is. Not surprisingly there are a bunch of crumblies in the bottom of the container I drained into no water but there is what appears to be rust particles. So knowing god helps those who help themselves it looks like spring cleaning time. Any pitfalls I should know about before I strip the carbs? Thanks for any wisdom.

 

[kevin-vic-b.c.]

Hello from Victoria, Last fall my 86 started doing the same thing.... I had lots of help from here but the end result was so simple it was stupid. In my clean up of the bike one day I knocked off the small rubber boot(cap) that plugged the "test Port" for syncing the carbs off the intake on one cylider. Check it out make sure there is no open ports.

 

I may be up in Vernon next summer for the aniversery of the Cadet Camp. My youngest son attended this sumer for 2 1/2 weeks for training. I have a buddy with some vintage (WWII) militarty jeeps and he may have me drive one up there for him for the 60th Aniversery so it is likely my son will return for more training also

 

Best of Luck

 

Ride Safe:canada::canada:

[Rocket]

Any pitfalls I should know about before I strip the carbs? Thanks for any wisdom.

 

 

Have you tried any Seafoam in the fuel system yet, it is available at NAPA. Try it before tearing down the carbs, you may not need to tear them down.

 

There is a few threads on site about methods on using it, use the search feature & look for Seafoam.

[CptKirk]

Gotta love that Canadian spirit Vernon's a great place for sun. That's why the bike no doubt. Buddy of mine is a Captain at the cadet Camp. Cpt. Steck. Sincere best.

Will try a carb flush of the bola see what else is in there and some Seafoam if I can find it at Walmart, two blocks to NAPA.

Tks large at least all agree I'm gong the right way.:dancefool:

[CptKirk]

The synch plugs are in place. They were there when I hooked up and their back now after I finished pulling sychrometer so no joy with a quick fix. Thanks for the thought :starz:

[CrazyHorse]

When mine backfired through the carb it did it with such force it actually unseated itself from the boot. Are all the boots tight on the carbs?

[rhncue]

The synch plugs are in place. They were there when I hooked up and their back now after I finished pulling sychrometer so no joy with a quick fix. Thanks for the thought :starz:

 

The carbs do need cleaned but where's all the rust in the bowls coming from? Tank is the only metal part in the system. I would get as much sediment out of the tank as possible and of coarse, change the filter and I might even put another filter in line. Chances are the tank needs to be de-rusted and resealed but that is quite a bit of work on a Venture pulling the tank.

 

Dick

[CptKirk]

Having a good look at the tank it's clean metal as far as can be seen with a small mirror BUT will be following the wisdom of additional fuel filter. Bike had very litle rust anywhere but some minor chrome pitting. The filter in it is not all that dirty when you backflush it. Looks like small grains of rust but they crumble in the fingers. Hope the seafoam and bowl flush helps but no biggie as if the carbs come off they are guaranteed clean. Just REALLY glad to hear the agreement on the carbs being the issue. :fingers-crossed-emo:fingers-crossed-emo

 

Boots are tight and no cracks on them at all. The backfire isn't violent but it's there and even though it hasn't been out yet (suspension redone incuding swingarm bearings (good shape but was in there cleaning anyways DOH .) it's not got much power dialed on.

[mbrood]

If the rust in the carb looked like mine...

http://bergall.org/temp/venture/carb-rust.jpg

 

You might look at the fuel overflow pipe... mine was pretty nasty...

 

The tank look ok but the inside of the overflow was rusted... tough to clean around that bend too...

[hipshot]

Having a good look at the tank it's clean metal as far as can be seen with a small mirror BUT will be following the wisdom of additional fuel filter. Bike had very litle rust anywhere but some minor chrome pitting. The filter in it is not all that dirty when you backflush it. Looks like small grains of rust but they crumble in the fingers. Hope the seafoam and bowl flush helps but no biggie as if the carbs come off they are guaranteed clean. Just REALLY glad to hear the agreement on the carbs being the issue. :fingers-crossed-emo:fingers-crossed-emo

 

Boots are tight and no cracks on them at all. The backfire isn't violent but it's there and even though it hasn't been out yet (suspension redone incuding swingarm bearings (good shape but was in there cleaning anyways DOH .) it's not got much power dialed on.

 

 

 

i may be talking through my hat, but i question the "two inline filters"!

i tried that once on a ford f-150, pickup, had NO power.

reason being that the fuel pump could not overcome the static resistance of TWO filters.

removed one and life was good again.

just jt

[Guest daveor]

Might be a dumb question, but do all your slides actually move when running? take the air filter off and look and see,, I had one that came undone,, been trying to recall what I did to fix it,, I know it was a diy fix. DAve

[CptKirk]

Picked up some Seafoam in both spray and pour in the tank variety. Plan to open the drains and spray some up into the carb bowls through the drain hoses and see what backflows out into a clean white container. The stuff that has come out initially looks lot like the pic of the crumblies out of float bowl above so will check the overflows for gumbo. Gotta say these drain hoses were a good design idea from the point of view that you an check the bowl contents and manually introduce a cleaner. But probably a messy pain in the butt for checking float level.

 

The slides actually don't move all together now that you mention it. The #1 and #2 are not responding the same as 3 and 4. I had the same though that they were torn or separated so pulled the covers and took the slides out along with the diaphrams and closely inspected hem. They are in good shape no tears or cracks and they are attached to one another like new. The springs are all good. All 4 of the jets in behind the diaphrams are clean and unobstructed. Pulled each out and looked down the passage ways which appear to be clear with no build up of garboly.

 

The overflow thing with rust is not a happy thing to have and cleaning could be a bear. Will pull the overflows and have a boo to see wassup. The tank fill neck has zip for rust as far as can be easily seen with a small mirror but sure can't see far inside. SO........... the overflow check is a great thought.

 

A second fuel filter is great idea and the thought of fuel pressure drop issues once installed is valid as well. Think I'll try it by jury rig and throw a pressure guage on the line to see what drop I get if any. Going to drain the tank as well an see wassup there too, it looks so clean I wasn't going to but it's well worth the check and know than trust the bedpan tank.

 

Thanks for the collective wisdom guys. Maybe I'll have this bike ready for a ride before he snow LOL. Interesting ebay experience expected some work on an old bike. Really could be worse.

Edited August 23, 2008 by CptKirk
clairity and spellling

[CptKirk]

Filled the carbs with Seafoam and let it drain. Got very little of anything from each so filled each again and closed the drains let the cleaner sit in the carbs for a day or two. Enough in there that it ran out of the overflow tubes on each. Got nothing out of the overflow tubes. The tanks has been drained and got nothing out of it to speak of at all. Caught the drain flow in a fine mesh. SO that's nice to know. Will drain the carbs in a while and then run some seafoam through mxed into tank fuel contents.

[CptKirk]

Well I let the Seafoam sit for about 5 hours as it's concentrated in the fuel bowls. I let it drain and no garbage came out with it but it was a very very slightly discolored fluid coming out into a clean white container. I refilled the tank with fuel and Seafom in a high concentration after reinstalling the fuel pump and new filter.

 

Only installed the stock filter at this point. I started the bike which it did right away (in a cloud of smoke:happy-emoticon:), allowed it to warm to off choke condition and ran it in the 2000 to 4000 rpm for a while,cycling the throttle to pump the mixture of fuel and seafoam through the carbs.

 

It doesn't backfire as bad but still does when cranked open for a second.. If I put my hand over one of the carb throats at a time the bike picks up RPM nicely with a 3000 rpm starting point so my question is...........

 

Does the airbox in place make a big difference in running?? Any restriction on the carb throats while running gives an instant increase in RPM. I guess I'll put it back on and see if there is a difference and take it back off to remove the carbs for a cleaning if it doesn't.

 

So............... do these bike run s(*&^y without the airbox? Never ran my 83 without it in place so just not sure if that is the issue at this point. :confused07:

 

Seafoam did improve things though.

Edited August 24, 2008 by CptKirk
clarity

[Rocket]

 

Does the airbox in place make a big difference in running?? Any restriction on the carb throats while running gives an instant increase in RPM. I guess I'll put it back on and see if there is a difference and take it back off to remove the carbs for a cleaning if it doesn't.

 

So............... do thse bike runs s(*&^y without the airbox? Never ran my 83 without it in place so just not sure if that is the issue at this point. :confused07:

 

Seafoam did improve things though.

 

Yup, runs much better with the airbox on..........

[CptKirk]

Did some searches on this site and the general consensus in returned hits is that the airbox makes a difference.

 

So I went to the parts I have cleaned up and pulled out the airbox. After a quick look at it I noticed that the velocity stacks are angled and can be angled toward the wallls and underside of the plenum chamber they sit in or angled toward the center opening to the air filter box. The assembled airbox has a compound purpose, air filtration and intake charge smoothing, velocity and containment of fuel standoff.

 

If they are angled toward the side of the plenum they are restricted by the side and roof of the plenum. That would restrict airflow and richen the mixture, if oriented toward the large opening to the airfiliter less restriction and a leaner mixture.

 

Now the million dollar question is which way do they point. If oriented toward the outside of the plenum in a more restricted area they serve the same as having my hand partially obstruct the carb throat and get a decent throttle response. Checked my 83 XVZ12 and they all point into the center of the plenum so will try that first. Does look like you can tune these stacks by orientation to change airflow characteristics.

 

Would appear Yamaha did some fluid dynamics research in designing the airbox and it has more to do with performance than just another air filter holder.

 

Since it's easier than sticking hot rocks up my B^&T I'll give it some experimentation.

Edited August 24, 2008 by CptKirk

[hipshot]

Did some searches on this site and the general consensus in returned hit is that the airbox makes a difference.

 

So I went to the parts I have cleaned up and pulled out the airbox. After a quick look at it I noticed that the velocity stacks are angled and can be angled toward the wallls and underside of the plenum chamber they sit in or angled toward the canter opening to the air filter box. The assembly part has a compound purpose, air filtration and intake charge velocity.

 

If they are angled toward the side of the plenum they are restricted by the side and roof of the plenum. That would restict airflow if oriented toward the large opening to the airfiliter less restriction.

 

Now the million dollar question is which way do they point. If oriented toward the outside of the plenum in a more restricted area they serve the same as having my hand partially obstruct the carb throat and get a decent throttle response. Checked my 83 XVZ12 and they all point into the center of the plenum so will try that first. Does look like you can tune these stacks by orientation to change airflow characteristics.

 

Would appear Yamaha did some fluid dynamics research in designing the airbox and it has more to do with performance than just another air filter holder.

 

Since it's easier than sticking hot rocks up my B^&T I'll give it some experimentation.

 

 

Kirk.

would you mind trying to translate that into english?

or something that us lay persons could relate to , without a dictionary?

lol

 

interesting idea, about turning the velocity stacks. let us know what you discover, please.

just jt

[CrazyHorse]

Did some searches on this site and the general consensus in returned hit is that the airbox makes a difference.

 

So I went to the parts I have cleaned up and pulled out the airbox. After a quick look at it I noticed that the velocity stacks are angled and can be angled toward the wallls and underside of the plenum chamber they sit in or angled toward the center opening to the air filter box. The assembly part has a compound purpose, air filtration and intake charge velocity.

 

If they are angled toward the side of the plenum they are restricted by the side and roof of the plenum. That would restict airflow if oriented toward the large opening to the airfiliter less restriction.

 

Now the million dollar question is which way do they point. If oriented toward the outside of the plenum in a more restricted area they serve the same as having my hand partially obstruct the carb throat and get a decent throttle response. Checked my 83 XVZ12 and they all point into the center of the plenum so will try that first. Does look like you can tune these stacks by orientation to change airflow characteristics.

 

Would appear Yamaha did some fluid dynamics research in designing the airbox and it has more to do with performance than just another air filter holder.

 

Since it's easier than sticking hot rocks up my B^&T I'll give it some experimentation.

 

On the bottom of the airbox there are lineups for the stacks a little rubber on each stack goes in a corresponding "holder" is the best word I could think of.

[CptKirk]

Sorry Hipshot got carried away.

 

Found this info and makes a lot of sense (dictionary included LOL)

 

Noticed some fuel spit back (stand off) without the airbox so its actually spitting out fuel during intake pulses. With the velocity stacks, plenum and airbox in place the intake is re ingesting the fuel stand off or spit back which richens the mixture.

 

Hey learned something new.

 

Credit for following to Wikepedia.

 

A velocity stack is a generally cylindrical tube with a radiused inlet end device which is added onto the air entry location or locations of an engines intake system, carburetor or fuel injection. It can be attached to an airbox inlet or to each cylinder in an IR (individual runner). Used with or without an "airbox". It is designed to:

1. Allow smooth and even entry of air into the intake duct with the flow streams boundary layer adhering to the pipe walls.

2. Modify the dynamic tuning range of the intake tract by functioning as a small reverse megaphone which can extend the duration of pulses within the tract.

3. Alter the dynamic tuning speed (dynamic engine compression) if the overall length is changed thereby changing the tuned length to a lower or higher rpm.

http://upload.wikimedia.org/wikipedia/en/d/da/Velocity_stack.GIF

Modified engines often have the original air box and associated ducting removed and velocity stacks are installed as aerodynamic replacements.

Modern fuel injection systems with a single air inlet typically incorporate some sort of tapered entrance, nullifying what gains might be had from a true velocity stack. However in professional motor racing where even fractions of a percent improvement count, this small improvement is welcome. The length of the stack is known to have a direct effect on a particular engine rpm range. As a result it’s not unusual to see a race engine with differing lengths of stacks to fine tune each cylinder. “Racy” in appearance, velocity stacks do not usually have a major impact on airflow or performance unless the stock horn is of an inferior design.

Beyond air flow improvement a velocity stack may be useful in containing "stand off" which may result from removing the original ducting. "Stand off" is fuel which is spit back out of the intake by pulsing action in the intake system. A velocity stack gives the engine a chance to re-inhale that fuel which can be helpful.

http://upload.wikimedia.org/wikipedia/en/8/8a/Velocity_stack_workings.GIF

The acceleration of air flow into a duct is inherently a highly efficient process and the difference between even the crudest radius inlet, and the most aerodynamic shape possible is slight, amounting to no more than a few percent. The flow coefficient of a perfect entry would be 1 while the flow coefficient for a sharp edged entry would be .9. A difference of only 10% from the worst possible entrance to the best possible entrance. This does not mean that engine airflow would increase 10% as the inlet end is usually not the smallest part of the system. The actual overall gain would be much less.

One of the current issues (2008) affecting velocity stack design on IR (individual runner) engines is that what an engine wants, to improve power, is may be different in radius and taper from what radius and taper flows best on an air flow bench but these effects are close to unmeasurable.

Edited August 24, 2008 by CptKirk

[CptKirk]

On the bottom of the airbox there are lineups for the stacks a little rubber on each stack goes in a corresponding "holder" is the best word I could think of.

 

I see what you're talking about. Gotcha and tks large. In place the stacks orient to the center of the air filter opening. Beauty.

[CptKirk]

This is the bike I'm working on. Following the wisdom from members of Venture.org (Which is more wisdom than the manual.)

 

Ebay in Canada.Was origionally from MI USA then to Winnipeg and on this site when I bought it. Front end needed work so the entire font suspension is rebuilt using help from the people here. (Never seen so much oil on a set of brakes. ) Have had it to the frame and wiring to clean up and get to know it.)

Also a picture of my 83. Fun bike to ride.

Edited August 24, 2008 by CptKirk

[Bob Myers]

My 86 sat for a long time with gasoline and no conditioner in it. When I started riding it a few weeks ago it did the same as you describe. Flat spot at about 1/3 throttle, another flat spot around 2800-3k no matter where the throttle was. I ran Klutz fuel additive through it, about half a can on the first tank and the rest of the can on the second tank. During the second tank it started clearing up and idle was higher each time I stopped(when i picked it up the idle was so low it would chug and die so I idled it up a bit). After finally getting the idle back down and running a second can through just for good measure all the popping in the exhaust and backfiring in the carbs has stopped. Backfiring in the carb is indicative of lean and popping in exhaust is indicative of raw fuel dumped in the chamber. My take on that is at least 2 of my carbs were messing up, one fat and one lean. After a very quick 3400 mile ride(4 days) it is as smooth as it was when it was ridden every day.

[CptKirk]

After the long winded B*&^%()t about velocity stacks and fluid dynamics.

 

I CANNOT believe how well this engine runs now. Absolutely like Dr. Jeckyl and Mr. Hyde.

Never seen such a transformation. Sure wouldn't mod an airbox on a Venture.

 

Airbox in place and it purrs like a kitten. Put the synchrometer back on and leaned the primary circuit back to the factory 2 turns from bottom. Didn't have to touch any other adjustments and it's bang on. In fact the vacuum is higher by 60 Kg/cm 2 and is at 250 KG/cm 2 all four carbs.

 

So the stacks are a huge part of the performance on the bike or what?

 

Very driveable now and from the widom here I can look forward to better yet

 

Now if I can only get he crankcase vent pipe connected without standing on my head.

 

LOL:bang head:

[Squeeze]

...

Now if I can only get he crankcase vent pipe connected without standing on my head.

 

LOL:bang head:

 

 

Take a long Needle Nose Pliers and grab the Hose with the Tips from the left Side of the Bike. Move the bottom Part of the Airbox slowly over the Carbs and attach the Hose first. Then mount the Airbox to the Carb-Throats, then the Filter then the Top Cover over the Airbox.

 

I've tried it several other Ways, neither worked out for me.