Engine running rich. I need help. Black spark plugs

[manduria]

Hi guys,

I have a '72 Yamaha xs2 650 that I restored. It has carburetors mikuni bs38 (clean new diaphragm), new tank, new air filter.

It also has new spark plugs but, they turn black and greasy on the ends. I believe the mixture is rich.

How do I fix that? Should I change the needle high (currently on position 3), or change the jet max, or what? Are there some outer screws I should adjust?

thanks

EDITED: I previously wrote bs34. Now I have corrected it. Thank you for pointing that out.

 

[TwoManyXS1Bs]

1- Change to BP7ES plugs
2- Are you sure that your carbs are BS34, not BS38?

 

[5twins]

Yes, you are running a #8 plug which is colder. The 7's may burn nicer, cleaner, and you may not need to fool with the carbs.

 

[grizld1]

Right! Heat range is read by looking at the ground clip of the plug; the clean-burn line should be about halfway down the clip. In your pics the whole clip is covered by deposits, indicating that the plug is too cold. Back in the day it was common practice to run a hotter plug for day-to-day running around, and to switch to a colder plug for highway use.

The "P" designation denotes a protruded nose plug, which is a later plug design. The protruded nose places the tip farther into the intake stream for cooling, resulting in a plug with an extended heat range, so that the need to switch plugs for different kinds of riding is pretty much eliminated.

 

[5twins]

The B8ES was the specified plug for these bikes when they first came out. Yamaha changed that recommendation after the first few years to the BP7ES. Notice how the tip and porcelain hang out the bottom of the threaded portion more than on the ones you're using now .....

 

[manduria]

Sorry my carburetor is BS38 mikuni solex , I found ngk b8es from Yamaha service manual , xs2 '72. I will try new bp7es for my bike

...thank you all

I will update after trying.

 

[5twins]

Yes, an early service manual will spec the B8ES. That was updated and changed to the BP7ES later, after that old manual was printed.

 

[MplsMurr]

I was in the same boat. My 2 cents, get the BP7ES (XS650Central recommended). Assuming you have Uni filters, like I do, change main jet. For carbs, I did a 1 and 3/4 turn, if I remember correctly. This fixed the way mine ran, increased throttle response, and sounds a whole lot better.

 

[uncle meat]

My plugs looked similar. I turned the mixture screws all the way in, counting how many rotations so I could go back to it if needed. Start with 1 1/2 turns out on each carb, fire up and check plugs. To lean out, turn mix screws in doing 1/8 to 1/4 turns. I used carb cleaner to clean plugs off after each adjustment. Take it for a spin around the block after each adjustment.
FYI, my air filters are stock so I didn't need to mess with anything else as far as jets, etc.

UM

 

[weaselbeak]

Does it idle ok? If so, drop the needles down. If not, fix the float height.

 

[manduria]

Hi ,
The shop in my town doesn't have NGK BP7ES. It has BPR7EIX, the seller tells me that with resistive it's better than normal. What can I do ?

 

[grizld1]

One thing you can do is to be patient and order the BP7ES, unless your bike has been fitted with electronic ignition. The seller's advice indicates that he doesn't know much if anything about breaker point ignition systems.

 

[Michaelo]

This might help, use the side bar to get further information from the link

http://www.ngk.com.au/spark-plugs/technical-information/spark-plug-anatomy-construction

 

[manduria]

I'm finally able to update you!
I got my new BP7ES plugs and now when you give it gas it doesn't loose power, but it seems to me the mixture is still rich. Any thoughts?

 

[grizld1]

The Peanut Gallery won't like it (they're all so eager to share that one-step fix that worked one time), but my advice is this: troubleshoot the ignition system thoroughly before you even think about playing with the carburetors. That means ohming out the coils, checking power delivery to coils and points, checking the condenser, and inspecting point gap and timing. The Tech button is your friend. BTW, the clean-burn line on the electrode is a bit wider than I like to see it; timing on that side may be a bit too far advanced.

 

[manduria]

The Peanut Gallery won't like it (they're all so eager to share that one-step fix that worked one time), but my advice is this: troubleshoot the ignition system thoroughly before you even think about playing with the carburetors. That means ohming out the coils, checking power delivery to coils and points, checking the condenser, and inspecting point gap and timing. The Tech button is your friend. BTW, the clean-burn line on the electrode is a bit wider than I like to see it; timing on that side may be a bit too far advanced.

Thank you. It is a little bit out of my comfort zone, but I will try. It will take some time for me to report back. What's the correct reading of the coils?

 

[grizld1]

Trying to work without a manual, are we? I've been turning wrenches on motorcycles for over 50 years, and wouldn't even think about trying that. I'm not going to repeat what others have already written up well, but I'll tell you where to look. Go to www.biker.net and download the relevant bits of the factory service manual--it's free. The version of the manual available there covers 1978 forward, but the instructions for troubleshooting and adjusting the breaker point ignition apply to early models as well. Also click on the Tech button here, you'll find a lot of relevant material. Pay attention to posts by Pamco Pete on inspecting for voltage drop from battery to coil, etc. BTW, be sure cam chain tension and valve lash are correctly adjusted as well before you mess with the carbs.

 

[manduria]

Thank you for your suggestions, Grizld1. It helps knowing where to look because my English is very limited. Between the actual information and the dictionary to translate, it seems I will have a lot of reading and learning to do. I will report back.