It's established it's either fuel delivery or a compression problem.
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Yamaha XS 650H Special II Exhaust Problems?
- Thread starter IamTheMarcus
- Start date
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- Tags
- exhaust restoration
It's established it's either fuel delivery or a compression problem.
Apparently you didn't read the part about him looking in the float bowls and finding them all gummed up. He was running the bike like that until it up and quit. That pretty much guarantees he has sucked all kinds of gunk into the passageways and plugged things up. I was taking carbs apart when I was 14. Are you saying today's youth are inept, stupid, and have no mechanical skills? Sounds that way.
IamTheMarcus,
I made up a thread that may help you a lot, (in conjunction with the members here), Especially read the links in posts 16/17 , the manual page is for the early bs38 carbs so don't use that as a reference for your BS34's. There are links in post 5 to later manuals, (G/SG H/SH), that have the BS34's in them
This thread will help you a lot so keep it bookmarked, lots of learning links spread through out the thread.
I made up a thread that may help you a lot, (in conjunction with the members here), Especially read the links in posts 16/17 , the manual page is for the early bs38 carbs so don't use that as a reference for your BS34's. There are links in post 5 to later manuals, (G/SG H/SH), that have the BS34's in them
This thread will help you a lot so keep it bookmarked, lots of learning links spread through out the thread.
IamTheMarcus
Young & Dumb
The engine ran well about a month ago when I was actually riding it around, at this point in time, both cylinders fired fine. And before I obtained the bike, it was sitting in a barn for at least 10+ years without maintenance.
IamTheMarcus
Young & Dumb
I will not be able to check the compression until my dad's friend finds his compression tester.
IamTheMarcus
Young & Dumb
All of that was cleaned, I was very vague on the description of the cleaning we did, although we went very thoroughly in cleaning it. (Taking out those parts you described)
IamTheMarcus
Young & Dumb
The bike was never run with the carbs being gummed up. So we had to take them off and clean them before the bike would even start. It may partake to you guys that I may be inept or stupid, though I find an interest in motorcycles, this motorcycle is the first motorcycle I've ever had, so I actually don't have much mechanical skills, but I understand what you all have been saying mostly.
no I was saying that it is irresponsible to propose stripping complex components to correct a fault when you haven't first tried to ascertain what the fault is through some basic non-intrusive testing first .
You don't know for sure that it is a fuel delivery problem!
it takes seconds to check the spark plugs to get a definitive picture of how a cylinder is running and get something diagnostic.
Stripping carbs because you suspect a fuel delivery problem without first doing some basic visual checks like..... fuel in the tank, fuel tap turned on, blocked or reversed fuel filters, blocked pipes, fuel on the spark plug after repeated starting attempts etc is dumb.
I just checked the spark from the spark plugs and they seem to be sparking fine, although I have about 1/6 of a tank of my 3.9 gal tank. I will be filling up my tank tomorrow, due to me winterizing my bike since up in Wisconsin it's pretty cold
Post 3 and 8
Until then you can stick your thumb on the spark plug hole while the motor is turning and see if you feel pressure. If there was a hole in the piston or valve you'd feel little or none. If you don't feel any pressure, problem solved
During that test wrap a wire around the threads on that plug and attach the other end under some random nut to ground it. Not having the threads grounded with the motor turning can hurt the ignition coil. Also I think that;s one of the tools you can borrow from parts stores. They make you put a deposit down and when you bring it back they return all the deposit.
What does the left plug look/smell like when you pull it? A failed diaphragm on the vacuum petcock is common. Remove the vacuum line from the LH intake manifold, block off the port on the manifold. (short piece of rubber tube and a bolt work fine) run the petcock in the prime position. Does that change how it runs? Where in WI are you?
IamTheMarcus
Young & Dumb
The left plug, when taken out is black, rubs off on to your fingers, and smells like gas.
I also live in Sun Prairie.
I also live in Sun Prairie.
So it's not too likely to be a plugged idle circuit. Smell your engine oil too. Check that petcock as I mentioned.
I could stop and look some time. There is a guy real good with 650s that lives in Sun Praire also he might be willing to help out a bit.
I could stop and look some time. There is a guy real good with 650s that lives in Sun Praire also he might be willing to help out a bit.
IamTheMarcus
Young & Dumb
Done, I felt quite a bit of air pushing out. This is without the throttle open at all..
IamTheMarcus
Young & Dumb
> Smelled the Oil, it's a little dirty, but it's starting to smell like old varnished gas I guess you can say. Color is still a bit goldish. (Will be changing it probably before the bike gets put down for the winter.)
> I plugged up the intake from the manifold, and it seemed to run normal, with just the right cylinder firing..
> When would you have the time to come check it out? I'm guessing it would cost a bit of money...? Otherwise where could I contact this Sun Prairie 650's guy?
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IamTheMarcus
Young & Dumb
Okay so, there was finally enough warmth to take the bike out of the garage, put it into gear and ride it around a tiny bit. It's not generating much power, just on the one cylinder working. I know this because I have to give it quite a bit of throttle to pick up a speed and before I actually gain the speed the left exhaust lets out a huge backfire, probably loud enough to compare it to a gun shot. :/
When you worked on the carbs did you remove the float valves and change the O-rings or install new float valve bodies? those O-rings are almost always rock hard and allow fuel to bypass the valve flooding the cylinder. did you set float heights?
IamTheMarcus
Young & Dumb
We didn't put any new parts into the carbs, just cleaned them, the float heights were at the correct height. (Probably should of bought a kit to rebuild it.. :/)
On the carb rebuild kits. the brass parts that come in the kits are generic. They may or may not be what you need.
Mikuni built BS34 carbs for many bikes, Probably atvs and snowmobiles as well as watercraft. Each application needed slightly different parts. The kits come with parts that work in some applications.
Best to tear down, clean, inspect what you have then order just the parts you need.
www.amckayltd.com/carbguide.pdf will help you on this.
Leo
Mikuni built BS34 carbs for many bikes, Probably atvs and snowmobiles as well as watercraft. Each application needed slightly different parts. The kits come with parts that work in some applications.
Best to tear down, clean, inspect what you have then order just the parts you need.
www.amckayltd.com/carbguide.pdf will help you on this.
Leo
It sounds like you have extreme flooding of the LH cylinder, do not keep running the engine like that, washdown loss of lube on that piston, thinned crankcase oil etc. IMHO those carbs need to come off again. I'd be willing to bet on a bad o-ring, let us know what you find. A "will fit" oring can usually be found at the local auto parts store.
