Carb jetting question

[flynvy5]

Ok guys and gals,

 

I'm running down a rabbit hole. I just rode 410 miles yesterday and on the way home i found the bike would seem to stumble in 5th gear 75 -80 mph. Almost like it couldn't decide what carb circuit to use. Had plenty of power. I'm wondering if i should rejet the carbs. My current setup is K&N filters in stock airboxes, Reinhart mufflers with the baffles, carbs are stock as far as i know. I did balance them this year.

 

I'm also thinking of using the same size jets in every carb. Has anyone tried this?

 

I would like to keep the fuel economy but i didn't like the feeling of it acting like it was stumbling. I'm hoping i'm not having a fuel pump issue starting. I have recently changed the fuel filter but i have done 3k+ miles since the change and didn't notice it on that trip 2up with a trailer. Yesterday i was solo with 3 friends.

[Patch]

Ok guys and gals,

 

I'm running down a rabbit hole. I just rode 410 miles yesterday and on the way home i found the bike would seem to stumble in 5th gear 75 -80 mph. So we don't know the rpm? I think on the Vtwin like 3000? In this case we usually divide the throttle 1/4 - 1/2 - 3/4 with masking tape then take it for a spin. At what position is the stumble compared to the tape marking?

Almost like it couldn't decide what carb circuit to use. This is more evident on a V twin and can be float related, but can be partially clogged jets as well.

Had plenty of power Like after it caught it's breath?

I'm wondering if i should rejet the carbs. Only if the the mains are worn. This sounds easier to find out than it is. The best way is to remove them and look closely at the shape of the main jet port, it must be perfectly cylindrical. The needle must be in perfect shape with no distortions or ware marks, or they will leak.

My current setup is K&N filters in stock airboxes, Reinhart mufflers with the baffles, carbs are stock as far as i know.

I did balance them this year.

 

I'm also thinking of using the same size jets in every carb. Has anyone tried this? Not recommended for air cooled V twin, the rear should be richer.

 

I would like to keep the fuel economy but i didn't like the feeling of it acting like it was stumbling. I'm hoping i'm not having a fuel pump issue starting. I have recently changed the fuel filter but i have done 3k+ miles since the change and didn't notice it on that trip 2up with a trailer. Yesterday i was solo with 3 friends.

 

I think I worked on one of these a couple of years ago? I do remember the rear jug had stuck rings and that carb I had to replace due to ??? Any how I couldn't rebuild it, can't remember what it was..

 

As for the exhaust pipe the problem started long after the change?

 

Let me know if I can help

Patch

Edited July 26, 2018 by Patch

[XV1100SE]

4th or 5th gear and "stumbling" could be a sign of fuel starvation. Under extended higher rpm if the pump is failing you'll get this issue. Mine started doing this and eventually it progressed to the point where the bike would stall. Wait 5 minutes and it would restart but then fail again shortly after.

 

Rejetting? May not be required. I run K&N air filters in the billet air boxes and have stock exhaust. Others with the same set-up and slip-on mufflers haven't had to rejet.

[Patch]

Yes I agree the pump could be at fault.

re jetting to me does not necessarily mean upping the sizes. Rebuilding verses simply cleaning would mean re jetting.

Having the baffles in place would indicate there is still back pressure so, likely the scavenging loss is minimum therefor, compensating with larger jets would be for other gains. I wouldn't worry about it in this case and increasing sizes wouldn't allow you to maintain your other goal of fuel mileage.

 

To check the pump you first check pressure _ around 4lbs (typical) then volume which I don't have the numbers for on your bike.

 

What's the mileage of the bike?

[Patch]

I had some time to look up the bike specs is this the model you have?

 

https://www.totalmotorcycle.com/photos/2009models/2009-Yamaha-V-Star-1300Tourer

 

Mikuni dual bore, 40mm returnless-type throttle body fuel injection system with TPS (Throttle Position Sensor) and ISC (Idle Speed Control) . This is a “closed loop” system that utilizes an oxygen sensor. The oxygen sensor feedback info to the ECU which in turn adjusts the fuel/air mixture for maximum power with minimum emissions. The oxygen sensor is located before the mufflers, so the use of slip-ons will not effect this system. Bore size is 40mm and each injector features 12 holes and a dual spray pattern for better fuel atomization and more complete combustion chamber filling. There is one injector per cylinder. Fuel injection benefits include improved fuel economy, chokeless operation, reduced emissions, and smoother running.

 

If so no jetting and the fuel pressure will be much higher. Also a liquid cooled V twin

[Freebird]

I'm confused now. According to his signature, he has a '07 Royal Star Venture. In his profile, it says '09 VStar. Since he is mentioning carbs, I was assuming that he was asking about the '07 Venture. I guess we need to ask what bike we are discussing.

 

I would also be curious about any changes RECENTLY made. K&N filter, Reinhart mufflers, etc. are all mentioned but how long ago was that done? If it has been running fine with all the current setup and just suddenly started having problems, it is not likely caused by the jets. They didn't change.

[Patch]

Well at least I am in good company, was feeling kind of you know....confused, old and.....

[Rafterd]

I'm confused now. According to his signature, he has a '07 Royal Star Venture. In his profile, it says '09 VStar. Since he is mentioning carbs, I was assuming that he was asking about the '07 Venture. I guess we need to ask what bike we are discussing.

 

I would also be curious about any changes RECENTLY made. K&N filter, Reinhart mufflers, etc. are all mentioned but how long ago was that done? If it has been running fine with all the current setup and just suddenly started having problems, it is not likely caused by the jets. They didn't change.

 

 

He also mentioned putting all jets the same size and wanted to know if anyone had done that. That’s RSV. IDK.

[Patch]

Because we are confused doesn't mean the OP is, it does read as a legitimate complaint one might have.

Edited August 4, 2018 by Patch

[flynvy5]

I had some time to look up the bike specs is this the model you have?

 

https://www.totalmotorcycle.com/photos/2009models/2009-Yamaha-V-Star-1300Tourer

 

Mikuni dual bore, 40mm returnless-type throttle body fuel injection system with TPS (Throttle Position Sensor) and ISC (Idle Speed Control) . This is a “closed loop” system that utilizes an oxygen sensor. The oxygen sensor feedback info to the ECU which in turn adjusts the fuel/air mixture for maximum power with minimum emissions. The oxygen sensor is located before the mufflers, so the use of slip-ons will not effect this system. Bore size is 40mm and each injector features 12 holes and a dual spray pattern for better fuel atomization and more complete combustion chamber filling. There is one injector per cylinder. Fuel injection benefits include improved fuel economy, chokeless operation, reduced emissions, and smoother running.

 

If so no jetting and the fuel pressure will be much higher. Also a liquid cooled V twin

 

Steven,

Thanks but i dont' have the 09 1300 anymore i sold that to a buddy. This is happening on my 07 midnight venture.

[flynvy5]

I'm confused now. According to his signature, he has a '07 Royal Star Venture. In his profile, it says '09 VStar. Since he is mentioning carbs, I was assuming that he was asking about the '07 Venture. I guess we need to ask what bike we are discussing.

 

I would also be curious about any changes RECENTLY made. K&N filter, Reinhart mufflers, etc. are all mentioned but how long ago was that done? If it has been running fine with all the current setup and just suddenly started having problems, it is not likely caused by the jets. They didn't change.

 

yeah sorry i forgot to update the profile. The 09 VStar was sold about 3 years ago.

[Patch]

 

I would also be curious about any changes RECENTLY made. K&N filter, Reinhart mufflers, etc. are all mentioned but how long ago was that done? If it has been running fine with all the current setup and just suddenly started having problems, it is not likely caused by the jets. They didn't change.

 

No problem. The above questions would be a good start.

 

Also just because we are now in the range of 3800 to 4000 rpms can you check that the ignition advance is still hooked up.

 

Mention anything out of your usual experience that comes to mind, you never know what that might suggest to us, helps us build a more complete picture.

 

I'll read up on your model