missing R 100 RT 1994

[grumpyone]

We got a missing 1994 R 100 RT. The girl just had the twinmax treatment and shows on the meter to be very good in the carb world from that.
Run it down the road a while like 15 miles and then stop and park in the garage a difinate miss feeling is there slow and fast idol.
Also does not seem like the engine has enough compression.
Can this be from timing?? Valves adj wrong?? bad rings?? or does it sound electrical ???
I would have thought if it were valves or rings the miss would have showed up by keeping the twin max from sync. ???
Any feedback or good guesses apreciated.
Thanks much
Jim and Esther

 

[jforgo]

Did you check the carb diaphragms?

 

[NEALART]

Go ahead and check that timing.

 

[sumran]

I would check your coils and the heat paste on your electronic ignition unit.

There are several things it could be. These are more likely to cause problems on a warm engine than a cold one.

 

[BRICKRIDER]

I would check your coils and the heat paste on your electronic ignition unit.

There are several things it could be. These are more likely to cause problems on a warm engine than a cold one.

This would be where I would start.

In addition to the coils & heat paste, check spark plug wires and all spark connections in this loop.

No guarantee that the problem is electrical, but evidence therein is pretty good. If any of these components need to be replaced, use factory OEM.

BrickRider

 

[grumpyone]

spark ohm ?

Brick. We tested the spark wires on the r 100 and came up with 4.83 which I think I remember there supposed to be 5000 so I am at 4830, on the R 80 I checked it to compare the wires on it go to 4.97 or 4970 pretty close to the magic number I remember of 5000. ? Would the numbers point to a problem on the R 100 or just a need to update in the near future???
I reset the valves today with about 500 mi after doing everthing on the carbs and valves and all and found the intake was tighter than sat at 500 miles ago?? I would guess since the bike had not been riden in a while much at all for say a couple of years this is probally just crud working off the valve and seat? ?
This bike is also very very hard to start cold compared to the 80 You have to choke it and get it just right or it wont run and keep the choke on for a good while. The temp is mild here right now. The 80 fires up no choke and runs in 30 sec down the road. ? I would guess maybe timing.? I did notice the 80 and 100 come with identical jetting in the carbs from bing?? I would have thought the 100 would have needed a tad bigger jet to run equally well?
Thanks for all the help
Jim and Esther

Plays with guns for a livin
Works on Scooters for Fun

 

[BRICKRIDER]

Brick. We tested the spark wires on the r 100 and came up with 4.83 which I think I remember there supposed to be 5000 so I am at 4830, on the R 80 I checked it to compare the wires on it go to 4.97 or 4970 pretty close to the magic number I remember of 5000. ? Would the numbers point to a problem on the R 100 or just a need to update in the near future???
I reset the valves today with about 500 mi after doing everthing on the carbs and valves and all and found the intake was tighter than sat at 500 miles ago?? I would guess since the bike had not been riden in a while much at all for say a couple of years this is probally just crud working off the valve and seat? ?
This bike is also very very hard to start cold compared to the 80 You have to choke it and get it just right or it wont run and keep the choke on for a good while. The temp is mild here right now. The 80 fires up no choke and runs in 30 sec down the road. ? I would guess maybe timing.? I did notice the 80 and 100 come with identical jetting in the carbs from bing?? I would have thought the 100 would have needed a tad bigger jet to run equally well?
Thanks for all the help
Jim and Esther
Plays with guns for a livin
Works on Scooters for Fun

Jim,

Spark
I believe that the wires and coil are the same for the R80 & R100, with only the plug being different. The resistance you found is pretty close to the right number. If it was my bike, and I was going to keep it, I would replace the spark plug wires just on general principal of being close to 30 years old. Funny things happen to electrical components when the age factor sets in. That way also one variable is taken out.

Coil
Coils are tough. They last a long time under rough conditions. They can test good in the garage and then go out on the road and when hot can start to break down causing engine miss. The only true test for an "iffy" coil is to substitute a known good one. They ain't cheap either. I've got a brand new Bosch coil that I carried for years in the fairing pocket as an emergency spare and never needed. You can have that one for half of dealer new cost if you wish. PM me if you want to pursue that option.

Intake Valve
I think you are right that some carbon is just burning off and that's why it closed up a bit. Would not worry about that at all. It's when the exhaust valves start closing down quickly that the end is near and time for valve job. I would say you're ok on that one for now. Keep in mind that in nearly 120,000 on my 83 R100RT, the valves went out like clockwork every 40,000. If you have not yet removed that goofy system that adds air from the airbox directly into the exhaust head, do so now!

Carb
It sounds like someone has tinkered around inside the carbs. Without checking, I'm quite sure that the jetting is different from R80 to R100. I know that the R100 went through a lot of jetting changes itself due to the EPA squeezing things. What I recommend is that you buy the carb book from Bing International and do a complete rebuild of both carbs on the R100. Replace floats, needle & seat, all gaskets & o-rings, and diaphragms. If you have access or know someone, while you have everything stripped out of the carb body, have it boiled out to remove any gunk, varnish & crud from passages. The book will tell you what the correct main jet is supposed to be, as well as the clip setting on the needle jet. Be really careful upon reassembly, as there are right & left parts, particularly in the choke system. The book should cover all of that clearly. Suggest doing one carb at a time. If you have a digital camera, take a few pictures of the most critical areas as they come apart to facilitate reassembly.

Timing
You can check timing with a strobe light, but in all the years I rode the RT, the timing was never off one bit. Unlikely that it is wrong on yours either unless somebody deliberately changed it. If the bike has more than 75,000 on it, a timing chain, sprockets and tensioner replacement are likely due.

Once you work through all of these things, 99.9% of the symptoms you are getting will likely disappear.


Brick

 

[AnnapolisAirhead]

I reset the valves today with about 500 mi after doing everthing on the carbs and valves and all and found the intake was tighter than sat at 500 miles ago?? I would guess since the bike had not been riden in a while much at all for say a couple of years this is probally just crud working off the valve and seat?

Jim, you did set the valves with the engine stone cold, right? First time I did it (doubt its your first time) I let my bike cool off, but it wasn't stone cold. I had a miss not unlike what you are describing. A fellow airhead suggested I reset the valves stone cold and that took care of it (they actually were off a bit from the first setting). also, my bike (at 58k) had been sitting for 8+ years in the garage, so I figured it also needed to be ridden a good bit, change oil & filter, ride 1000, change oil & filter, etc.

Now it all runs really well, although the valves have an ever-so tiny tap. Tom Cutter wrote an article on the bevel on the valves wearing (rounding) and that if its running well, its most likely fine. Unless you are a perfectionist and want to throw in a new set of valves, there is nothing wrong with this. All of his articles I've read have never lead me astray.

I also replaced the wires. Cheap insurance that they are ok.

Good luck.

 

[lkchris]

... in all the years I rode the RT, the timing was never off one bit.

Because timing doesn't "go off" unless someone moves it off.

The new BMW electronic ignition is pretty bulletproof and extremely strong (it can kill you) and I'd consequently look for fuel problems. Diaphragms. The fact it "takes a lot of choke" to start indicates very lean mixture, vacuum leaks, etc.

 

[shire2000]

Had the same problems on a friends R100 last month. Pulled the carbs apart and numerous of the little "O" rings had hardened up and 2 had become squared off. Replaced them all, cleaned the jets out (yet again), reset the floats to ensure they were set right. Once all back together, without even fiddling with anything else, it ran much smoother. Then did a quick and dirty carb balancing (by ear). Runs smoother than his wife's R80, lots of power and no more missing, coughing, farting, spitting, etc. Tamed the beast.

It is a known issue with these Bing carbs that the o-rings go bad if left for any lenght of time. They are relatively cheap and easy to replace. I do mine every few years, just because.

 

[grumpyone]

Kent

Thanks for the info. A bit more info from me might be in order. At national we got a complete rebuild kit for the carbs and they have been done. The twin max carb sync machine says they are great.
The bike has had one prev owner but the question and main concern IS someone has messed with the entire bike WAY to much. We have reciepts for work done after work done that is ? able. Anyhow we were concerned the thing has been repaired to death. Timing may be off because of this being adj by the po's mechanic? We are also 6000 ft higher in elevation than original.
Would elev. create timing change necessary? would not think so but?
To give an example of the amount of things this girl has been throught, a new arm., diode , three sets of fork seals, trans rebuild, and on and on and it only has 55 k on it. ????
Anyhow I thank you for both your wise feedback and (spelling corrections)
Some might take things wrong, I take all wisdom given as a gift.
Thanks
Jim and Esther

 

[BRICKRIDER]

Higher altitude does not require a timing change.

Leaner carb settings are needed. The Bing manual should have some info on carb settings for altitude. If not, or if you do not have the manual, then you will have to do trial & error.

Start with a leaner main jet. I hate guessing this stuff and would rather be guided by a manual. The carb changes the fuel mixture according to throttle position by several different subsystems in a coordinated manner. The main jet is the simplest to undo. The process is too complex to discuss through a forum, so I really recommend the manual.

As I mentioned in my last post, check the timing just to eliminate that variable. I'm starting to wonder about PO's mechanic.

3 sets of fork seals is unusual. Is bike is ridden in a very dirty or buggy environment? If so, fork gaitors may be necessary. Otherwise, seals were either installed wrongly or wrong seals were installed.

New rotor & diode board is normal.

Brick

 

[lkchris]

Since the diaphragms move less due to thinner air at altitude, Bings are considered altitude self adjusting. Jet changes not critical. Recent bikes are pretty lean to start with.

VERY VERY more likely missing is caused by lean condition and it's hardly ever caused by rich condition (which is theoretically what occurs at altitude). In addition, owner notes bike is hard to start cold which is an indication of lean setup.

New carb kits don't mean there aren't vacuum leaks at carb/head connections nor does it mean there isn't restricted fuel flow from tank to carbs. It doesn't mean the needles are in the proper notch.

Proper valve adjustment and good compression are givens.

 

[BRICKRIDER]

Since the diaphragms move less due to thinner air at altitude, Bings are considered altitude self adjusting. Jet changes not critical. Recent bikes are pretty lean to start with.

VERY VERY more likely missing is caused by lean condition and it's hardly ever caused by rich condition (which is theoretically what occurs at altitude). In addition, owner notes bike is hard to start cold which is an indication of lean setup.

New carb kits don't mean there aren't vacuum leaks at carb/head connections nor does it mean there isn't restricted fuel flow from tank to carbs. It doesn't mean the needles are in the proper notch.

Proper valve adjustment and good compression are givens.

Kent,

Thanks for providing the additional info. Carbs were never my forte, and outside of guidance from a good manual, I don't care to mess with them other than to verify that any wear & tear items are up to snuff, and that the internal passages are clean.

BrickRider

 

[grumpyone]

Up Date "gas"

The problem may be solved We hope. The gas had alchol added for condensation and it appears the mix of h2o alch in the bowls are pretty high. I am guessing this is what I am seeing. It is like water but with a swirl not a bead effect like without the alch in the tank. We will remove replace and put in new screens and see if that does not fix it.
Thanks for all
Jim and Esther

 

[kstoo]

Oh, good, I am glad that you found yer RT. I thought that is was still missing. Wow, you must have been frantic while it was gone.



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