Yamaha Starbike Forum banner

1 - 20 of 47 Posts

·
Registered
Joined
·
9 Posts
Discussion Starter #1
So I just picked up a 1998 v star 650 with pretty low miles and on the way home on the freeway I can't get it to go above 60 mph. WOT in 4th and 5th and they both won't go above 60. It also feels like its lacking power in general when accelerating. Give it a lot of gas and it feels like it cuts the power. On top of this it has aftermarket cobra pipes and it backfires a lot.

Replaced the air filter today- no difference in anything.
Pulled spark plug and its black on the end but not too bad. Gonna have those replaced tomorrow and test plug wires as well.

Don't want to take the carbs off and get them jetted and tuned and that not solve my power loss.

Any advice is much appreciated. I'm mechanically inclined and understanding of engines so tell me what you guys think this could be. :)
 

·
Registered
2006 Stratoliner, 2014 Triumph Rocket III Touring, '81 XS650SH Project
Joined
·
576 Posts
Hello Bugyt and welcome from Virginia.

With low miles on a known reliable engine like the 650, this issue does seem to be more of a fuel delivery matter. Seafoam is great but not a miracle worker always on the first go. I have seen it gradually fix old fuel issues over 2-3 doses.

In the end though, you may have to rebuild the carbs. Luckily these are not the hardest to rework.

I see this is your first thread, if you don't mind, go over to the Introductions area and tell us more about your riding past, especially if you work on or rebuild these machines. Oh, and lots of pictures, we are a visual lot.
 

·
Super Moderator "Loose Nut"
Joined
·
7,989 Posts
Definitely sounds like main jets are clogged, especially since you didn't mention any lower RPM issues. Give the Seafoam a chance to work before you dig into the carbs. The carbs are pretty simple but can get frustrating if you're not comfortable doing it.

97079
 

·
Registered
Joined
·
567 Posts
So I just picked up a 1998 v star 650 with pretty low miles and on the way home on the freeway I can't get it to go above 60 mph. WOT in 4th and 5th and they both won't go above 60. It also feels like its lacking power in general when accelerating. Give it a lot of gas and it feels like it cuts the power. On top of this it has aftermarket cobra pipes and it backfires a lot.

Replaced the air filter today- no difference in anything.
Pulled spark plug and its black on the end but not too bad. Gonna have those replaced tomorrow and test plug wires as well.

Don't want to take the carbs off and get them jetted and tuned and that not solve my power loss.

Any advice is much appreciated. I'm mechanically inclined and understanding of engines so tell me what you guys think this could be. :)
apologize if you already know this but the alcohol in ethanol gas sucks up water and gels out and has a short shelf life. Sounds like you have an older low mileage bike so it has probably sat idle for extended periods. The first attempt to start it will suck that gel into carbs and foul one or more jets. The Seafoam will sometimes do the trick after multiple treatments as mentioned in other posts. If not, there are good stepwise videos on carb rebuilding... let us know how you make out. Welcome to the forum, by the way. Also, it is not uncommon to need carbs re-jetted after an exhaust upgrade do to the change in system backpressure... do you know if it was done? Backfiring can often be eliminated by a small tweak of the PMS... search the threads for past posts on this.

 

·
Registered
Joined
·
1,679 Posts
And I will say it again, check the connection between intake manifolds and the heads, it is a thin O'ring and it leaks air easily. Everyone installs them dry,never check tightness and the o'ring gets hot and flattens out. a small air leak here really effects top end speed.Put something on the o'ring, I.E oil, vasaline,I use a thin amount of permatex, but something.
 

·
Registered
Joined
·
1,466 Posts
On the 85 Yammy Vmax I owned. I did a "shotgun cleaning." Meaning I used carb cleaner & pressurized air (from an air compressor) to clean the carbs.
The bike had been sitting for 3-4 yrs with what I call the e10 gas. (May have up to 10% corn ethanol mixed in.) So I took the parts off to exposed the carbs. Placed towels around the carb area & cleaned them.
Not sure I am not of how much of the carbs can be exposed on the 650. My suggestion may be moot because of lack of exposure.

Ride smart! Ride often!
 

·
Registered
Joined
·
9 Posts
Discussion Starter #10
Well I'll definitely try the multiple doses of seafoam and see how that goes first. I've worked on carbs before but prefer not too as I dont have the patience for them lol.

I know the carbs were never rejetted after the exhaust. So if it comes down to it does anyone know how much rejetting will cost me at a shop?
 

·
Registered
2011 Yamaha VStar 650
Joined
·
324 Posts
Do you happen to have pics of the spark plugs before you replaced them? In your first post you mentioned that they were black - this could indicate you bike is running rich and not lean... What do your spark plugs look like now? Similar in color? Or are they white (lean condition).
 

·
Registered
2011 Yamaha VStar 650
Joined
·
324 Posts
Possible that you have a sticking float in one of the carbs. I would recommend that you check your oil and make sure it doesn't smell of gas too. If you get gas in your oil you can destroy the motor.
 

·
Registered
Joined
·
26 Posts
Well I'll definitely try the multiple doses of seafoam and see how that goes first. I've worked on carbs before but prefer not too as I dont have the patience for them lol.

I know the carbs were never rejetted after the exhaust. So if it comes down to it does anyone know how much rejetting will cost me at a shop?
I had my starter clutch done a few weeks ago and that was only $350 in labor when I asked about doing the carbs at the same time he said add another $600-$800 but if I took them off it would only be $300 I’m up in Massachusetts everything is more up here
 

·
Registered
Joined
·
222 Posts
r $600-$800 but if I took them off it would only be $300 I’m up in Massachusetts everything is more up her
Ouch. Don't need to remove the carbs to clean the jets. You tube video, can do it yourself. If i can, anybody can! Take pictures. Use a JIS screwdriver, should be one in your tool kit.. Need some cab cleaner, and take your time. Or spend the 300-600 bucks. While you're at it replace the fuel filter too. Les is right, it really sounds like your main jets are clogged. If not, then cc&d jet chart for sizes to start... Ask and we can talk you through it, or check out the diy videos...
 

·
Registered
Joined
·
9 Posts
Discussion Starter #19
So I smelled the oil and it does smell like it has some gas in it so I think at this point I'm pretty sure the carbs need to come off and rebuilt but I'll have them rejetted as well to help the backfire. I'll be talking to some shops tomorrow and keep you guys updated once I get to the point of taking the carbs off to take to the shop.

I'll also look into the fuel filter but I don't think it's going to be that because if it was clogged then it wouldn't be running rich but more lean I feel like.

Thank you so far to everyone who has posted their advice and ideas.
 

·
Registered
2011 Yamaha VStar 650
Joined
·
324 Posts
Cleaning the jets and checking on the movement of the floats is pretty easy and there is plenty of decent YouTube videos on it. Worse part is removing the screws in the float bowls as they are JIS standard as @stratsurvivor mentioned - fortunately, there should be one of these screwdrivers in your bikes OEM tool kit. If you decide to clean the jets yourself, work on one carb at a time and take photos as you go. This way, you shouldn't mix any parts up or forget how to reassemble everything.
Also, make sure to change your oil and oil filter before running the bike again. Gas in your oil will play havok with the lubricity of your oil, which can lead to bearing failure. Better to change it than risk an expensive failure.
 
1 - 20 of 47 Posts
Top