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Topic-icon New Airhead Owner - Needs Help! (Lots of Images)

  • dretek
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3 months 3 weeks ago - 3 months 3 weeks ago #4733 by dretek
Fellow airheads, I am a new proud owner of a 1982 R65. This is my first motorcycle so I am not entirely sure what I am doing. I live in the Manassas, VA area. I got an aerospace engineering degree and have no idea how engines work, so here I am. Besides this project, my free time is focused towards skateboarding and rock climbing. Im interested in meeting other airheads so let me know!

Here is a picture of the bike:

A quick description (from seller):
16000 Miles. Features upgraded Marzocchi shocks, beefy K100 Forks, 34mm Vikuni VM Carbs. Bike has been serviced including: top end refresh, valve adjustment, final drive service, carb sync, etc.

I got this bike from a little shop in DC. Owner said it has been sitting for a long time.

The current problems I am facing:

• I am leaking fuel from the right exhaust nut

• Tiny leaks at the oil pan

• The bike starts fairly easily with the Mikuni chokes in the DOWN position (CHOKE OFF), however, after letting idle, and then revving the engine, the bike shuts off (see video).

• Bike shuts off when carb chokes are in UP position (CHOKE ON) and starts easier when carb chokes are OFF - a bit strange?

• The mixture screws were messed with, any advice on these Mikuni V34 Carbs?

My next steps are to:
1) Valve adjustment following this guide:
If gaskets looks good, I will probably keep them.

2) Check/replace "$2000" O-ring where oil is leaking

3) Check/replace seals around exhaust nut

Minor Fixes
1) Fix right indicator light
2) Replace center stand spring

Do you think I should go through all these tuning steps?
How can I fix some of these problems?
What are more good sources for information? Tuning equipment?
Is there anything I am missing? 

Tools/Equipment Needed:
Exhaust nut tool
Torque wrenches (in/ft sized)
Spark tester
Magnetic drain plug
Contact point set and condenser
Valve cover gasket

In other news:
I get my motorcycle license in two weeks.
Last edit: 3 months 3 weeks ago by dretek.

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3 months 3 weeks ago - 3 months 3 weeks ago #4734 by Wobbly
Welcome aboard !

Fuel is leaking out the exhaust because too much fuel is entering the combustion chamber, and that is a REALLY bad sign. That super "rich" condition means it needs immediate attention. Luckily it also means it's going to take more "searching" than "cash" to repair.

Going against you is the fact that not too many bikes get fitted with Mic carbs, so there's not going to be a lot of people to help you with the finer points of Mic tuning.

► Here's are some very general things to look at, in roughly the repair order...
• If there is that much raw fuel in the combustion chamber, then it has also managed to dilute your engine oil. CHANGE THE ENGINE OIL.
• If your fuel is over 8 weeks old then get rid of ALL of it. Yes, empty the tank, fuel lines, and carbs.
• If the bike isn't running, then the petcock(s) must be in the OFF (horizontal) position. That's according to the Law of Gravity.
• Remove the fuel lines from the bottom of both petcock(s). Petcocks often leak, but are rebuildable. Make sure fuel isn't passing the petcock(s) in the OFF position. A 12 hour test is needed.
• Find out how to set the Mic float level and check for the correct fuel levels in both carbs.
• Check the air filter and air filter housing for blockages. A clogged air filter will pull more fuel into the combustion chambers. A new air filter is usually a good thing.

► Mic fuel enrichening is: lever down = ON; lever up = OFF. Airheads always like a rich mixture to start, but then they prefer a slow sliding scale of 75% ON... 50% ON.... then 25% ON for the fist 2 minutes are so. So the Mic system, while simple, works against you. At some point in your digital fuel enrichening scheme you'll be forced to turn the enricheners OFF before the engine is really ready. At that point you'll need to rev the throttle gently to keep the engine running. DO NOT expect the engine to accept a regular idle until 10 miles of riding is completed.

► There are 2 screws on the Mic... Idle Mixture and Idle Speed. Don't get them mixed up. The typical idle mixture screw initial setting is 1-1/2 turns out.

Also see this tread....

Hope this helps.

Don't hide 'em, Ride 'em !!
Last edit: 3 months 3 weeks ago by Wobbly.

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  • dretek
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3 months 3 weeks ago #4741 by dretek
I'd hug you if I could, thank you so much for an immediate response. Before I change the engine oil, I will probably order a filter and a gasket online, so I can change everything at once. Is there an easy way to tell if it has an oil-cooler. I keep reading and re-reading snowbums article: and get really intimidated..

Also for draining the fuel, can I do that all through the petcock? I'm guessing the carbs have some valve where all the fuel can come out as well..

I will keep y'all updated with photos. This weekend I plan to empty and replace the fuel. Get tools and knowledge in preparation for an oil change (while I wait for parts to come in). Once parts come in I will change the oil, replace the filter, and hopefully change the $2000 infamous O-ring that still confuses me.

Also, does anyone know where I can get a Mikuni VM34 manual, kind of like a "Clymers" for this carb?

Blue skies,

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3 months 3 weeks ago #4745 by 14979
Hi Andre,
I lived in Manassas VA years ago, back when Dullas access was for the airport only :) Electrical Engineer for GE but the traffic drove me nuts, now I'm a hermit in Maine ;)

Doesn't look like you have an oil cooler. On my 1981 R100RT the cooler lines originate in the cover for the oil filter and the cooler is mounted on the frame cross bar in front of the front engine cover.

Fuel can go six months if it was treated with something like Seafoam. I store my bike every winter with a full tank and seafoam then drain the carbs. But it's probably safer to drain and dispose of that old fuel. There might be a drain on the carb bowls but I'd just connect a long fuel line to the petcock to drain into a container. Also if that is corn gas, it likes to suck up water so the brass pieces in the carbs might be green with corrosion. Pull the bowls off and have a look.

Also if you have that much excess fuel you may also have fuel in the oil. If you pull the dip stick and smell fuel, do not run the bike, replace the oil and filter first. . I'd change the oil and filter just outta hand since you don't really know the history.

I'd add a TwinMax or similar gauge to sync the carbs, it's very easy with the correct tools.
Best of luck and it's fun to learn new stuff!!


1981 R100RT

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  • dretek
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3 months 3 weeks ago #4747 by dretek
Thanks 14979. The traffic is nuts, luckily I lived opposed. Should I clean the bowls with some carb cleaner once taken off?

Im reading that the bike should run 15-20 minutes, to drain the oil >easier<. Is it absolutely necessary, given that the bike doesn't really run (nor do I know how to drive it)?

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3 months 3 weeks ago - 3 months 3 weeks ago #4748 by Wobbly
Some ideas...
• Mr 14949 is correct. Your third photo proves your bike does NOT have the oil cooler. (The oil cooler hoses begin and end at the oil filter cover.)

• You'll want to get the filter that has the same diameter "rubber" bushing on each end. This may be a one-piece filter, or the newer hinged filter. You'll also want several new white o-rings and gaskets at the same time. This stuff is so special you want to get it from someone who knows BMWs inside and out (not your local auto parts dealer). This is where I go...

• DO NOT even mess with changing out the oil filter until you completely understand what's being said about the white o-ring. You don't have an "oil leak", you have an oil residue left after riding hundreds on miles. You might be loosing a teaspoon every 6 months. Consider the risk factor of that loss relative to destroying your engine.

• An R65 has one petcock, so it's best to remove the tank and empty the old fuel into a pan. To be eco-friendly you can then pour that old fuel into your car. Your car will never notice it.

• Drain the carbs by removing the carb's float bowls using the 4 screws on the 4 corners. You need to look at the inside of the bowls anyway. If you see a brownish tinge, then you need fuel additive, like StarTron. Next autumn when you KNOW things are OK inside the carb, then you can use the far more convenient 19mm drain plug on the bottom center of the float bowl.

• Sudco sells all the after-market Mic kits and tools.

I'd hug you if I could...

Just fax a cold beer instead !! :P

Don't hide 'em, Ride 'em !!
Last edit: 3 months 3 weeks ago by Wobbly.

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