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Posted

I have just purchased a 1996 Royal Star with 20k km and this is my first V-4. The bike has every bolt in Chrome accessory and very clean. Now it has only had 70km put on it in the last 2 years. I have changed the fur out in it and have put 300km on it so far. Bike fires up and seemed to run very well at all. But if I bring tpm’s up while in neutral, it will start to back fire out the exhaust. When throttling up while riding it revs out pretty good. But when decelerating, it backfires out every exhaust it sounds like all the way down to slow rpm. Now for the bike from what I can see. It has aftermarket pipes on it so every cylinder has its own exhaust pipe, air box was removed and 4 K&N cone style filters fitted into all carbs and have checked the air/fuel mixture screw setting and is set at 4 turns out. I have not yet removed the carbs to clean and see the jets in the carbs etc. Wondering if anyone would like to give me some thoughts on this bike. I know my way around a tool box and bike but as I stated, new to the V-4 world. I am not a big fan of the air box being gone and do want to find one to get a box back on. Yamaha has dis-continued them and can’t buy new so may take a bit to find one. Thanks for everyone’s time and look forward to hearing feedback and thoughts on my bike. Love to get some fall km’s on before the snow sets in.

Posted

It's very likely that the cone filters and exhaust are causing the problems. I would look on ebay for the stock air box first. That might fix it. If not look for the stock exhaust.

Posted

I can always tell if Tweeks has a pin hole or a bad seal on her pipes as she will start backfiring at the first sign of fresh air being sucked into the exhausts.. Not that aftermarket pipes arent completely capable of being a good system as far as controlling such non-sense but a lot of times their "fit" isnt quite up to par with OEM - I think I would be looking at those first..

Posted

These CV carbs rely on the constriction afforded by the factory airbox. Without the airbox I'm a little surprised it runs/idles to any acceptable level.

 

You can get the OEM airbox, probably pretty reasonably priced as I'm sure someone here has a pile of then laying around.

 

There are two correct answers here that I'm aware of.

 

1. Replace factory air box. Should quiet things down a bit too. I run my Vmax with a custom airbox and the correctors, I can hear lots of throaty music that I would not like to hear after hours in the saddle.

2. Use the air corrector jets. Tiny brass plugs about the size of a pencil eraser, set of 4, they press right into the top of the carbs with no disassembly required. They fool the carbs into thinking that the restriction of the airbox is still there so that pods or free flowing setups can be used without going in and rejetting everything. In fact I'm thinking if your riding this thing around it already has those brass doodads added, or the tune was tweaked to make it sort of run. If they are there you should remove them before placing the OEM airbox back on.

 

I'm looking for a pic of mine but cant find it. If you post a top down pic of the tops of one of your carbs we'll be able to see if these jets are visible. (They dont go in or on the barrels, but a small orifice adjacent to the barrel.

 

Oh, and welcome!! Congrats on the fine steed.

Posted
It's very likely that the cone filters and exhaust are causing the problems. I would look on ebay for the stock air box first. That might fix it. If not look for the stock exhaust.

 

ye is do want to eventually find the air box and go back to it. Never have liked or trusted these type of filters. I do want to keep the aftermarket exhaust as I do like to hear my bikes. So going to have to figure that out if I can.

 

I can always tell if Tweeks has a pin hole or a bad seal on her pipes as she will start backfiring at the first sign of fresh air being sucked into the exhausts.. Not that aftermarket pipes arent completely capable of being a good system as far as controlling such non-sense but a lot of times their "fit" isnt quite up to par with OEM - I think I would be looking at those first..

 

Yes totally true. I am working on getting my carbs off to do a full cleaning and while

doing that I am going to check the tightness of all pipes. They show no signs of leaking but I guess you never know.

 

 

These CV carbs rely on the constriction afforded by the factory airbox. Without the airbox I'm a little surprised it runs/idles to any acceptable level.

 

You can get the OEM airbox, probably pretty reasonably priced as I'm sure someone here has a pile of then laying around.

 

There are two correct answers here that I'm aware of.

 

1. Replace factory air box. Should quiet things down a bit too. I run my Vmax with a custom airbox and the correctors, I can hear lots of throaty music that I would not like to hear after hours in the saddle.

2. Use the air corrector jets. Tiny brass plugs about the size of a pencil eraser, set of 4, they press right into the top of the carbs with no disassembly required. They fool the carbs into thinking that the restriction of the airbox is still there so that pods or free flowing setups can be used without going in and rejetting everything. In fact I'm thinking if your riding this thing around it already has those brass doodads added, or the tune was tweaked to make it sort of run. If they are there you should remove them before placing the OEM airbox back on.

 

I'm looking for a pic of mine but cant find it. If you post a top down pic of the tops of one of your carbs we'll be able to see if these jets are visible. (They dont go in or on the barrels, but a small orifice adjacent to the barrel.

 

Oh, and welcome!! Congrats on the fine steed.[/

 

i can’t attach pics yet as I am new. Otherwise I would love to know what these are as these are the filters I have for now. I do have one slide out as I was looking to see if the needle was marketed. It has no marlins but does have e-clip and a black plastic spacer with a little tit that goes into the slide. Anyone know if that could be original or aftermarket?

Posted

Surprised it hasn't been mentioned yet but...Seafoam might help with cleaning the carbs, and do a carb sync. Have you tried premium fuel? These bikes use regular gas (87 octane - or is it 89....whatever the lower one is). Put half a can of Seafoam Motor Treatement in the fuel tank and top it up with premium then give it a really good run.

 

I'd start with these three first (premium, Seafoam, carb sync) before tearing into it.

 

And welcome to the forum from Ontario !

Posted
Surprised it hasn't been mentioned yet but...Seafoam might help with cleaning the carbs, and do a carb sync. Have you tried premium fuel? These bikes use regular gas (87 octane - or is it 89....whatever the lower one is). Put half a can of Seafoam Motor Treatement in the fuel tank and top it up with premium then give it a really good run.

 

I'd start with these three first (premium, Seafoam, carb sync) before tearing into it.

 

And welcome to the forum from Ontario !

 

I only run premium in everything. I have given it s hard 300 km run fine the highway already and I would never date put sea foam in anything I own. If it’s dirty or a problem, it’s cones apart and gets cleaned.

Posted
The specs call for lower octane. Try a tank of 87 (or 89) octane and see if that makes a difference.

 

The problem in Canada is we have ethanol in our regular and it’s not good on our engines. It’s extremely hard to find regular without ethanol in it. I should try and find some and see if it makes a difference.

Posted
ye is do want to eventually find the air box and go back to it. Never have liked or trusted these type of filters. I do want to keep the aftermarket exhaust as I do like to hear my bikes. So going to have to figure that out if I can.

 

 

 

Yes totally true. I am working on getting my carbs off to do a full cleaning and while

doing that I am going to check the tightness of all pipes. They show no signs of leaking but I guess you never know.

 

 

 

i can’t attach pics yet as I am new. Otherwise I would love to know what these are as these are the filters I have for now. I do have one slide out as I was looking to see if the needle was marketed. It has no marlins but does have e-clip and a black plastic spacer with a little tit that goes into the slide. Anyone know if that could be original or aftermarket?

 

The black plastic titted spacer is OEM,,, Mom Yam's bold attempt at making the metering rod depth of engagement non adjustable. To fine tune by fattening up or leaning em down at the main jet can be accomplished by adding/subtracting nylon washers for metering rod height.. I do mine with washers from Ace Hardware but I do know that we have a member that sells "kits" for doing exactly that.. Skydoc is his name and he is a guru when it comes to this stuff.

BTW,, it only takes a pin hole or a faulty seal with a tiny leak to suck in enough fresh air and cause a lot of backfiring.. Those pin hole(s) can be small enough that they will go undetected as far as actual noise being emitted from them,,, dont take much of a leak to allow air in and BINGO = backfire!! :biker:

Posted

I too have backfiring issues and I am attempting to address them. Carb sync is up next in my quest.

 

But....my question is does the backfiring cause the bike any actual harm?

Even with my deceleration backfiring, the bike runs incredibly well.

Posted

I haven’t had a chance to do much work on the bike yet but I do have a stock air box coming on Tuesday for it. I need to know what the air correction jets look like to make sure I don’t have them in my carbs when I put back together. I can’t attach pictures yet since I have not posted enough on here. Does anyone have a picture they can post or a way I can talk to someone that knows if my carbs have them or not? I can email or text someone if they will know. Also from my research I have been doing, looks like the air cut off valves can also cause my backfiring on deceleration. Anyone had issues with these in the past?

Posted (edited)

Update: Tore carbs all down and cleaned. A lot of crap in the air bypass valves. Re assembled with Barron jet kit for stock air box with aftermarket exhaust. Took all the cone filters off and found a stock air box to replace. Replaced fuel filter. Did carb sync and running great at idle and up to about half throttle. After that it is dead. Backfires a bit then nothing at all. This thing has be boggles right now. Anyone have thoughts now? Also wondering if maybe there is air corrector jets installed? I don’t know what they look like or where they go.

Edited by Christoph
Posted (edited)

Id say carbs probablyneed to be rebuilt. You can try cleaning the first. For sure see if whoever installed the cones put in a restrictor plate. If not I'd go back to the factory set up for air. Sync up the carbs once you get the fuel/air straight.

Edited by ese
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Posted

Id say carbs probablyneed to be rebuilt. You can try cleaning the first. For sure see if whoever installed the cones put in a restrictor plate. If not I'd go back to the factory set up for air. Sync up the carbs once you get the fuel/air straight.

Posted

My guess on the bogging down part of your problem. Since you are back on the factory air box, I'd go through the cards and set them up. Start at about 2.5 turns out. If you have a way to measure air/fuel...do so for each carb. After that, balance them for air delivery....be advised the owners manual has the info incorrect as to what screws balance what carbs/carb bank. Proper info is found with a quick search.

 

Sounds like the P.O. may have adjusted the carbs a bit lean for the after market air filters and now you are way lean.....??? I'm not a carb guy so it could be the other way around. But I would bet once you get the mixture right and balance the carbs, she'll be back to normal.

 

Both procedures can be found with a search. I'm on the road so can't help much at the moment.

Posted
Id say carbs probablyneed to be rebuilt. You can try cleaning the first. For sure see if whoever installed the cones put in a restrictor plate. If not I'd go back to the factory set up for air. Sync up the carbs once you get the fuel/air straight.

 

all of this was done. Except I don’t know if there are any restrictors in it as I don’t know what they look

like. They cards were way out once I put them all back on but got them to sync perfectly after about half hour of playing around.

 

My guess on the bogging down part of your problem. Since you are back on the factory air box, I'd go through the cards and set them up. Start at about 2.5 turns out. If you have a way to measure air/fuel...do so for each carb. After that, balance them for air delivery....be advised the owners manual has the info incorrect as to what screws balance what carbs/carb bank. Proper info is found with a quick search.

 

Sounds like the P.O. may have adjusted the carbs a bit lean for the after market air filters and now you are way lean.....??? I'm not a carb guy so it could be the other way around. But I would bet once you get the mixture right and balance the carbs, she'll be back to normal.

 

Both procedures can be found with a search. I'm on the road so can't help much at the moment.

 

i have the air screws at 3 turns out as the Batons card kit said to start with that. The carbs were completely cleaned complete Barons carb kit installed that gave the new needles set on 3rd clip from top, new pilot jets and mains. Replaced fuel filter, got the stock air box on with new air filter and new spark plugs. Checked the setting of the TPS and was right where it was supposed to be. Now it idles and starts awesome. Great power to about half throttle. When I let off it comes back now smooth with no backfiring. But once you get above half throttle it is almost like you hit a rev limiter. Pip pops pip pops. Can’t get nothing. Let of and smooth as silk. Come right down to near idle then hammer on it, revs hard and then pip poppedy pip. I just don’t get it. I’m completely boggled.

 

Also I did notice when I plugged the TPS back in it and did a test between the blue and yellow and slowly twisted the throttle while the plug was plugged in, it smoothly climbed up to 1.6ohms and then changed directions and went back down. Also on last test drive I tried unplugging the TPS and did same test but acted exactly the same just with the check engine light on.

 

Anyone able to help or thoughts please do because I’m completely at a loss. Just plan old dead spot at 1/2 throttle up.

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