BS175 Dual twin, running on 1 cylinder..[SOLVED]

[Crazygreg]

Update:

Solved! was the crankshaft seal, replaced the crankshaft assembly, cleaned everything,  now it work perfectly, start first kick!
Thanks to everyone for precious tips, and all the great help!
Now, I have to get this new pistons\rings breakin correctly!

YEAY!

Greg


 
and the right cylinder smoke like crazy (look like professional smoke machine )
I changer the spark plug, nos Coils, condensers, re did all the electric connections, timing is perfect, cleaned rotary valves, head, piston, carburetors.., checked oil pump adjustement...and it still mainly run on the right cylinder!! grrrrrr!  
Does the magneto can afect the spark on one cylinder only??, it look like there is spark on both, but left one seems a little bit unstable (sometime stop for 3-4 rotations).
Regarding the smoke, the pump look clean, it look like it over deliver oil to the right cylinder as oil drip from the exhaust pipe junction!

Ideas welcomes!

Thanks!

[OldSwartout]

Check my response to your post in the  Members: Introduce Yourself thread.  BTW, very good looking bike. 

[Crazygreg]

Solved :

Didn't think about it right away, but air filter was quite dirty, as it probably have never been changed\cleaned...
not enough air for both cylinders...started the bike without it and it solved everything...

G

[Crazygreg]

Hi everybody!
Happy New Year first!
So I got tons of NOS part for my BS175, got it registred (was a pain as was without papers), insured, almost all cable changed (except the overpriced throttle one), timing check, new air filter (found the perfect replacement as an oil filter for cars), just needed to cut a hole in one side, but same diameter, lenght and paper type. Bike run pretty well when hot, but pretty hard to start!

One new problem : right cylinder seems to still run better than the left one, run a lot hotter, exhaust tube becoming a lot more yellowish than left and when I touch the muffler ends the right one is way warmer than the left one, can't let my hand on it, but ok on the left,  when I stop the bike, right exhaust rubber is smoking and start to have some tiny cracks...
Which kind of temperature should be at the end of the muffler?, are the exhaust tube yellow coloration normal.

G

[Toystoretom]

I'll bet your right cylinder is running lean....

[Crazygreg]

So finaly got my left cylinder replaced (chrome was gone)
THought it will solve my problem....but not.
Re-checking the timing...
Is there a mistake in the manual? saying that when the point close, the light is on... on mine is reversed (when the point close, light is out)...

[reed]

Crazygreg
You are right when the points are open the light you are using will be on.
When the light comes it should line up with the fire mark etc.
Thanks.
Steve.

[Crazygreg]

Thanks Reed. Oldswartout told me that they use a powered timing light...which is reversed (ignition off)
I re-did the timming perfectly, and then I followed Oldswartout check list (thanks a lot by the way); coil are good (these were new), points are good too, spark plugs are good.
When I start the bike with point cover open, there is small blue spark on the right points but not so much on the left point, sometime randomly a yellowish one, so my last option is probably a faulty condenser..will check this tomorrow.

[reed]

crazygreg
I do my timing  first with 12 volt bulb and then i run the engine.
Then i fine tune it with a timing light so its spot on.
So using a bulb and the points open the light is on.
Thanks.
Steve.

[Crazygreg]

 Hi,

So after making the timing perfect  ,  I followed all the check list with no success , I even replaced the condensers assembly just in case i missed something, re did a bunch of connections..now the spark is definitively stronger...but cylinder still run randomly (10% of the time) It doesn't make sense!! coils, points, condenser, spark plug, compression, everything seems good!
The current goind through the points when running (checked with a multimeter between condenser and engine body on both points) is 10V, spark jump 8mm (over 1\4") quite easily bright blue as well... I still have two question though :
- is blue wire providing electricity to both coils? or is the electricity come frome separate generator's  coils by the white and the black wire? (so those are not only straight wires)
- if my problem is not electric, can the seal in the middle of the crank act as a one way valve and let the right cylinder suck all\part of the mix from the left crankcase cavity? is there a way to check that it is in good shape without opening the case? this is my last idea, i replaced the worn left cylinder (which probably worn out since the left is almost never warm and didnot expand at all), both pistons, rings, base gasket, new coils, new connectors, battery is new and charged,  switched carbs, checked valves position...no luck! is this bike cursed? 

[OldSwartout]

Wow! Good job going through all that. 

The blue wire supplies power to both coils, I think it splits someplace near the coils.  The white and black wires lead from the coils to the points.

You can check the center seal by pressurizing one side and see if it leaks into the other.  You have to plug two of the three openings:  the intake, exhaust and spark plug and pressurize through the third.  Whichever is easiest with whatever parts you have lying around will work.  Don't use high pressure, 10 psi or less is enough.  You may have a leak at the seal on the left end of crankshaft, not the center.  Either the left seal or center seal leaking could cause a problem at idle and low speed, but are unlikely to be bad enough to cause it to run badly at higher speeds.  Does the problem clear up if you rev the engine to 4-5000 RPM? 

Beats me.... 

[Crazygreg]

The bike idle really well on one cylinder, helped by some random runing on the left, doesn't seems to clear out at high rpm, even though it doesn't have too much difficulty to rev up...it is not really powerfull for taking off in 1st gear, I have to rev it to get it to have enough power and then it go but with a lot of difficulty. I do not want to try it too hard as the ring \piston are brand new.
 will check the left exhaust pipe to see if it's not obstructed by something. Will check the leak, and will replace the seal on the left side too!

Thanks

Greg

 

[old smokey]

Hey? I posted something here and it didn't make it?
Crazygreg - verify that the left condensor wire lead to the points is on the correct side to the points and isn't being insulated by a phenolic washer (assuming it's anything like a GTR points or points on a CB360T). My dad once did that on the 360T and let the bike sit for years before I took it and found the problem why it was running poorly on one cylinder. Good luck.

[Crazygreg]

Thanks everybody for all your nice tips! 
 I followed oldswartout pressur experiment, and the seal appear to act like what i was guessing : kind of like a one way valves! probably one of the lip is worn.
The right cylinder sucks the left cylinder mix (mostly air probably) when left crank case pressurise  and that explain why the right is so warm (lean).

I used a small leath to create a tight plastic with oring sealed plug on the valve cover, and let the plug on the left, removed it on the right, moved left piston on top dead center blow 10PSI in and air was comming out from the right cylinder plug hole...

Anybody have an idea on where to get a good crank\seal assembly for a not crazy price?

thanks again! this forum is great! 

[reed]

Crazygreg
I would try Richard or Kevin(scrambler) they may have a good used crankshaft for sale!
Good luck.
Steve.

[OldSwartout]

Anybody have an idea on where to get a good crank\seal assembly for a not crazy price?

thanks again! this forum is great! 

What serial number is your 175?  I have a spare seal for the early crankshaft before 16B, but none for the later one. I'll replace the seal for a reasonable price ($30 + seal), but getting the seal is the problem.

[Crazygreg]

thanks a lot Oldswartout!
Unfortunatly, my 175 is serial 16L21193  engine TA1-21332. 
At worst I will try to find a new crankshaft and If I can get a new seal.  then get the seal replaced on mine (6800 miles on it) and sell it for a reasonable price to pay back the new crankshaft.
Can I install any 175 crankshaft into the case? (is it just the inner diameter of the seal changing?)
Is there any newly made sealed bearing at the good dimension that could replace the seal (by removing one side of the seal?)

Thanks

Greg

[coxy]

there is a nos crank on ebay it is expensive at around $250.00

[OldSwartout]

thanks a lot Oldswartout!
Unfortunatly, my 175 is serial 16L21193  engine TA1-21332. 
At worst I will try to find a new crankshaft and If I can get a new seal.  then get the seal replaced on mine (6800 miles on it) and sell it for a reasonable price to pay back the new crankshaft.
Can I install any 175 crankshaft into the case? (is it just the inner diameter of the seal changing?)
Is there any newly made sealed bearing at the good dimension that could replace the seal (by removing one side of the seal?)

Thanks

Greg

There is a difference in the bearings.  The early crankshaft had a normal roller bearing in the center.  The later one had a bearing with a dowel pin locator that kept the bearing from rotating or moving sideways. The crankcase bearing bore had the dowel pin, the bearing outer race had a shallow hole for the pin to engage + it had a couple through holes to let lube into the bearing.  The seal ran on a sleeve next to the bearing. I think the sleeve was to keep the bearing inner race from moving.  You could use the earlier crankshaft, it would be necessary to remove the dowel pin from the crankcase bore.  In that case, I'd definitely loctite the outer race in position at assembly.

[Crazygreg]

Solved! (see top)