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Old 11-21-2010, 08:41 AM   #1
jrunberg OP
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Oddometer: 99
Airhead help needed (please :)

I have a Frankenbike R60/5 that I'm trying to get moving well again. And while I'm not the biggest idiot in the world I'm also not the most experienced... And and all help/suggestions are appreciated!

First: deets on the bike.
  • R60/5 SWB
  • PO swapped in a R75 engine/carbs
  • has new (and tested) coils, wires, condensor, points
  • all grounds and wire contacts cleaned and tight
  • compression check (dead cold) is 120 left and 117 right (carbs on hooked to air filter assembly). No leakage after 5min both sides.

Work done about a month before the problem started:
  • The spark looked weak so I replaced the coils/wires and cleaned all the wiring connections on the bike.
  • A good shop (Velocity in Richmond, Va) cleaned the carbs, set the valves and timing, checked and replaced the condensor / points a month or so the problem started.
  • New battery as well

Now for the problem. This started while on a local ride and it was a sudden which then got a bit worse as I rode home on surface streets. Bike now won't get much above 25-35mph. Starts easily but clearly is unbalanced.
  • Somethin's wrong w/ the right cylinder. No power, head / exhaust temp is cool compared to the other side. Temps measured w/ an IR thermometer show 300+ left side and half that on the right (measured at the exhaust nut).
  • If I swap the wires left / right the symptoms are the same.
  • If I replace the plugs (stock spec NGK) and run it the left plug is a decent tan while the right plug is black and wet (looks like fuel, not oil).
  • The right side exhaust smells of raw fuel. If I let it warm up enough you can hear fuel popping in the right side exhaust.
  • Choke position on the right carb does nothing. Same running whether it's in or out.


I could use some insight here. My best guess is the electrical unburnt fuel smell, lack of choke effect. I'm not too clear how this would affect only the right cylinder (my experience lies in VW aircooled engines), however.

My preference is to use this bike to learn on instead of simply taking it to a shop. Any and all help is appreciated!!
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Old 11-21-2010, 08:46 AM   #2
kixtand
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Sounds like a major fuel related issue to me. Double check everything on the carb, to the point of unhooking all cables and starting over.
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Old 11-21-2010, 08:58 AM   #3
TimTowtdi
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You might try swapping the floats from one carb to the other. Also make sure they are adjusted correctly. With the bowl off and the fuel on, fuel should quit flowing then the casting line on the float is parallel with the body of the carb.

dave
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Old 11-21-2010, 09:00 AM   #4
mark1305
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Plus one on checking cables, especially to make sure nothing has snagged the choke cable and pulled it out of the ferrule at the end. I'm guessing Bing carbs? If so, I'd drop the bowl on that carb and work the floats up and down while working the petcock on and off as needed - check that the fuel entering the carb shuts off just as the floats approach parallel to the carb body/bowl flange.

Normally, a stuck float needle would cause overfolow onto your foot. If by some chance your carbs don't have the overflow tube and/or have the pivoting alcohol-resistant floats installed (which I understand don't use a bowl with an overflow tube).

My Bings do overflow on my feet, but when it happens, the symptoms are much as you describe.
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Old 11-21-2010, 10:20 AM   #5
Lokey
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Just a thought.....

There have been quite a few comments regarding the crappy Chinese points/condensers that are commonly sold for airheads. Since the problem started after a tune up that included new points, try installing the old points/condenser back in the bike and see if that changes anything.

You could squirt fuel into the dead cylinder and see if it picks up and runs on that side. If it does, then it is a fuel delivery problem, although since the plug is wet I don't think that is what is wrong.

Before you do anything check the valves.........
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Old 11-21-2010, 10:35 AM   #6
Country Doc
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I've had all kinds of bizarre running problems caused by points closing up. Especially if they were replaced recently, as they wear in quickly and then settle down after their initial "break-in".

Worth checking, along with the suggestions above.

dc
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Old 11-21-2010, 04:55 PM   #7
jrunberg OP
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Progress...

Thanks to everyone for thoughts and suggestions -- a few minutes this afternoon allowed some progress...

Pulled the bowls to check the floats. Floats appeared to work fine fuel did not flow when they were horizontal. But MAN was there some crap in those bowls! I don't remember that being in there!

Cleaned both bowls and made sure both orifices were clear (neither were on the right carb). Drained the fuel from both sides of the tank and -- low and behold -- water and all sorts of fine silt/residue. Interesting that it appears that the fine stuff got through the new filters that were fitted below the petcocks. Since I don't have any new plugs I pulled the right one and wire brushed it before putting it back in. No pitting or galling -- just DIRTY.

After buttoning it all back up and putting in some relatively fresh gas she fired right up (like normal) but is running better...
  • choke works on the right side now
  • head temp (by the plug) is now even at 460deg on both sides. It's idling fast and we weren't going anywhere...
  • while it's still not perfectly happy the temp @ the exhaust tips are a lot closer and she runs more evenly. Exhaust pulses feel almost the same on both sides.

So over the next few weeks it looks like I'll be re-cleaning the carbs after checking the valves and timing (to be sure).

One question... after about 20-25min of idling the exhaust headers glowed RED for the first 6" after the heads. I've never seen this before on my other bikes -- makes me think she's running really rich to cause that (although I have no real idea). thoughts?

john
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Old 11-21-2010, 05:04 PM   #8
rufusswan
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If you clean the tanks then clean the petcocks.

Don't let it sit and idle for 20+ minutes without a good cooling fan. You risk burning it up. The bike is built to RIDE! not idle.
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Old 11-21-2010, 05:17 PM   #9
fishkens
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Nice work on tracking down the problem. Sounds like the fuel line may have been clogged?

Quote:
Originally Posted by jrunberg
One question... after about 20-25min of idling the exhaust headers glowed RED for the first 6" after the heads. I've never seen this before on my other bikes -- makes me think she's running really rich to cause that (although I have no real idea). thoughts?
john
20 - 25 minutes?!?! Like rufusswan says, that's waaaaaaay too long w/out a big fan blowing on it.
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Old 11-21-2010, 05:56 PM   #10
mark1305
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Yep. Glowing headers after prolonged idle usually means overly rich, thus allowing afterburn in the headers - espcially if your engine has the air injection setup plumbed in at the exhaust ports. Conversely, overly lean mixtures can sometimes also cause it from elevated exhaust gas temps.

Because prolonged idling & glowing headers has led to a few fires on some fully faired models (including some later models and other makes IIRC), some legal disclaimers have been added to rider manuals recommending no warmup, but just ride off moderately for the first few miles.
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Old 11-21-2010, 07:58 PM   #11
jrunberg OP
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Oops. Probably won't let it idle **quite** that long next time.

Polishing up a new tank and will switch that on over the weekend. And then... try and ride it.
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Old 11-22-2010, 06:03 AM   #12
bpeckm
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Glowing red at idle ?!? Something is definitely wrong, there. Temps should get hot, but not THAT hot.

As suggested, look for an air leak problem (75/5 engine would not have air injection), most likely place is the carb-to-head boot area. The fast idle would also be an indicator of a manifold/vacuum leak. That would be where I would look, first: easy.

Then make sure your valve clearances are adequate, as well. Takes a little more time, but should be checked, for peace of mind if nothing else.

Good luck!

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