High idle / valves?

[FREEMANR100RT]

I adjusted the valves for a r100rt (1980). I decided to change out the spark plugs at the same time. After the proceedure the idle at running tempature incresed from 800-1000 to 1800-2000.

My original maintenace plan was to adjust valves , add new plugs, adjust timing and then rebuild carbs and resync. The intention was to do these projects one at a time over a few days but the high idle is going to prevent me from properly setting the timing.

I thought that I might have set the valves improperly so I redid them and they are spot on over and over. Could the adjustment and / or the new plugs make that big a difference? I am leery of resyncing the carbs if I made a mistake with the valve adjustment.

My intention now is to resync the carbs to lower the Idle so that I can adjust the timing; and then rebuilding the carbs and syncing again.

Am I missing something? Any advice would be greatly appreciated.

Thanks,

Sean

[sumran]

Welcome. I also have a 1980 RT. Is the bike new to you and do you know the history of the bike? How did it run before your adjustment?

It is possible that the valves were out of adjustment before and someone elevated the idle to compensate for it. If so, your valve adjustment would have caused the idle speed to be too high. Have you tried to lower the idle speed with the adjuster screws to get it back in range?

Rebuilding the carbs is not a bad job, but it is expensive and having some experienced hands and eyes around is helpful for the first attempt. Do you know they need rebuilding or are you doing it so that you will be sure they are good? If there are known problems with carb internals, that would change the answer to your original question.

Properly adjusting the carbs is built on simple steps, but it is an art that can drive you crazy if you are not familiar with these machines. If you can find a group of airheads in your area they will be a great help to you. It is likely that someone close by has a great understanding and feel for the process. Most are happy to help and share knowledge.

This forum is helpful and there are many smart folks that post here to help guys like me. If you can't get hands-on help from local airheads, you can get good information here. But it has the typical limitaions of electronic exchange.

Best of luck.

[FREEMANR100RT]

Thank you sumran

I bought the bike a few months back and she was riding mildly rough. The carbs leak so I bought the needle, floats and rebuild kit ($75). My "clymer" manual and the advice I've read here suggested doing these maintenances in order.

It is possible that the valves were out of adjustment before and someone elevated the idle to compensate for it. If so, your valve adjustment would have caused the idle speed to be too high. Have you tried to lower the idle speed with the adjuster screws to get it back in range?

I did not want to adjust the Idle speed with out being prepared to resync the carbs properly. Can I toy with these without the vacum guages attached?

[sumran]

The carbs can be adjusted without a vacuum gauge and many prefer to do it that way. There are a few methods. I like to do the fine tuning with a vacuum balance tester. Getting the valves right is the right place to start. Also, be sure your points are properly adjusted and the timing is correct.

What was included in your rebuild kit? A complete kit is much more expensive, but there are several variations of partial kits.

The order I use in adjusting carbs is as follows:

1) Valve adjustment
2) Float level
3) First idle speed adjustment (must be close to adjust mixture)
4) Idle mixture adjustment
5) Final idle speed adjustment
6) Throttle cable adjustment

Carb adjustments must be made on a fully warmed engine. Be sure to keep air flowing over the cylinders with a high volume fan to avoid overheating. To check balance without a vacuum gauge, short out one side of the engine, then the other and compare speed. If you take the ferrules that you did not use with your new plugs, you can attach a length of spoke or all thread to them. Thread this on the plug and put the plug wire on the other end. The you can ground out the plug to the cylinder with a screwdriver to kill one side of the engine at a time.

You can build a vacuum balance tester. You will want it to be close to adjusted before you use this tester. If it is way out of adjustment you pull fluid into the side with the stronger vacuum. See this link: http://www.airheads.org/content/view/183/98/

I would glad to call you and offer what help I can. PM me with your phone number if that is helpful.

[108625]

Sean,

Since this bike is new to you, you might want to look back at what you've done so far and make note of it while it's still fresh in your memory. Things like:
1. How much did you have to adjust each valve, and were they tight or loose?
2. What did the old plugs look like? Was the gap way too wide due to electrode erosion, did they show signs of running rich or lean, were they even correct for the bike?
3. When you get to the carbs, note where everything is set before you take them apart. check your cable adjustments, too.
You are going about things in the right order, just taking some notes along the way might help you figure out what is behind the results you are getting.

Bob

[DennisDarrow]

Sean.............

To properly warm up the bike for a carb sync/idle speed adjustment, ride it for about 10 miles. Time to quit worrying about the valves. You did good.

First though, it's easy to check the timing. This can cause idle problems and it is best to get your valves right, then points/timing, and THEN do the carbs.

For now, just screw out the idle screw, the big ones a little on each side, after a proper warm up, to get the idle down to the 1K range.

Then, check the timing with a light. Some folks will recommend using a seperate battery or power supply. Not necessary but possibly a good thing.

If your timing is OK, then procede on to the carbs. If not, disconnect the battery and pull that front cover and dig in to the points. Let's hope that the timing is right and then you dont have to fool with that.

Do some searching for "carb sync"...............Good luck.......Dennis

[44006]

"I adjusted the valves for a r100rt (1980). I decided to change out the spark plugs at the same time. After the proceedure the idle at running tempature incresed from 800-1000 to 1800-2000.

My original maintenace plan was to adjust valves , add new plugs, adjust timing and then rebuild carbs and resync. The intention was to do these projects one at a time over a few days but the high idle is going to prevent me from properly setting the timing."

===============================================
I assume you did not mess with the carbs at all up to this point

Can you confirm there is freeplay in the cable at each carb and that the idle speed
is actually determined by the idle stop screw and not the cable adjust position?

If the cables are covered by rubber boot at carb end when messing around the
bike it is easy to pull one upward inside the boot so it lands on the top of the
adjuster pocket instead of dropping onto the socket - this of course will rev the
engine up at idle

[FREEMANR100RT]

Thank you all for your advice. I went ahead and build the $4 carb sync and did a rough sync to even out the throttle speeds and lower the idle.

the problem I am having now is that my left side back fires on occcasion when I release the throttle.

Is the mixture too rich? The sync details on the $4 sync article did not state how to determine the mixture setting. Should I play with the mixture?

Also the sync device is even when at idle but when I apply the throttle it significantly increases on one side. Is that normal?

[20774]

The mixture is not set using the manometer...not necessary anyway. With the engine running, free play in the throttle cables so you're at idle, you slowly adjust the mixture screw...first turn CW until the cylinder stumbles (you're starving the cylinder of gas) and then CCW until it stumbles again (you're richening the mixture). Find the spot in between these two points and then turn the mixture screw another 1/8 turn CCW to make it slightly richer. Repeat on the other side.

You're supposed to now ensure you have the same idle speed on each side...I suppose the manometer could help there. If you have to make adjustments to the idle speed, go back to the mixture and repeat the steps. This is an iterative process to get the settings just right.

After all that, then you need to check the cable tension just off idle using the manometer.

Besure and have a fan blowing air on the cylinders during these steps. It could take 3-5 minutes or more to get this done. You don't want to overheat the engine.

[88bmwJeff]

You're getting a lot of good advice here. It's possible that the bike needed proper tuning and that's why it was idling low (at least until you adjusted the valves and replaced the plugs). FWIW, I have an 88 R100 RT, and when I replaced my coil, the RPMs went up 200-300 RPMs. The old coil was not allowing a good spark.

Since the bike is new to you, I would concentrate on making sure all parts are in good working order, and adjusted properly--rather than trying to compare the performance before, during and after tuning up the bike.

When you get around to rebuilding the carbs, I would do one at a time, and use the other one for a reference. This way you wont mix up parts.

[DennisDarrow]

Also the sync device is even when at idle but when I apply the throttle it significantly increases on one side. Is that normal?

The indication you are refering to is the whole purpose of the manometer. Whether when adjusting idle or throttle cables. Two different procedures of course.

It is kind of counter intuitive for this ol dyslexic; but the side that pulls down is the stronger running side and it is actually the other side, or often both that needs adjustment.

When adjusting the idle you want to see them change as you adjust the mixture screw and then when they are at their best reading, the lowest on the manometer, they should match.

Kurt mentions about turning the mixture screw an eighth of a turn CCW to get rid of the popping. Try one carb at a time on a test ride. It usually happens when you are decelerating/downshifting at a moderately slow speed. Make the adjustment on one, see if it helps, stop, set it back the way it was and see if the popping comes back.

The manometer is truly valuable for when you are just beginning to roll the throttle open, as you describe one cylinder is pulling harder than the other. The cylinder that indicates the lower position needs to be given perhaps not even a quarter turn of slack(CW turn). Be careful as you tighten up the lock nut as this often changes the very sensitive setting. I find that even 1/16 of a turn will bring changes. After you get the roll on right, from idle to say 1500 RPM, take it on up to 3000 or so. Some folks dont agree about this; but for me, after learning to do it from a very old wrench from the fatherland, assures me that it is smooth at the RPM that I ride at.

Please, before you make these adjustments, take the bike for a 10 mile or so ride to warm it up...........TOTALLY IMPORTANT...............

For me, the fan in front of the engine works; but I would rather make a few adjustments for a couple of minutes, take it for a ride, and then come back and make a few more. To often perhaps, folks think that the fan will provide cooling for 15 minutes or so of adjustments...............to me this is wrong...........

Anyway.........glad you are obviously making progress.............Hang in there......Dennis

[manicmechanic]

I would also advise observing your tach when tweaking the mixture. First set the balance and idle speed, then rais the idle speed to maybe 2K, using both idle speed screws. Now adjust the idle mixture screws one at a time and observe the tach for the highest speed. Once you've achieved this, then back out the mixture screw that 1/8th turn. Then reduce the idle speed and rebalance at idle, and check off-idle too. Only takes a couple minutes but works well for me.

Also make sure all your air connections are tight, as in the intake boots. I'm guessing it's not backfire, but maybe a little afterburn in the exhaust.

[AnnapolisAirhead]

Congrats on the bike. Should have tons o' fun with it. Sounds like really great advice from the folks here.

For whatever its worth, the Bing Carb manual is invaluable and a helluva good deal at $10, direct from Bing's website. I found it helpful to read the tiny numbers on all the carb pieces and matched them to the Bing book--then set things. Its a safe thing to do, as we found out trying to sync a friends R100RS MotorSport--the jets were not the same on both sides so someone had messed with it. These bikes are older and a lot of hands have probably touched them, so its safe just to verify IMO. Also, if you haven't already started on the carbs, I found it easier to do one at a time as some parts are 'handed'.

If one side if still backfiring, you might want to double check that the choke is actually off by pushing the lever on the carb down (not just the choke lever on the handle bar (or airbox). Sometimes they get sticky, were re-assembled incorrectly during the last carb rebuild, etc.

Setting the valves should be done with a stoned cold engine,right? I pull the valve covers off at night, leave a small pan under each cylinder to catch the bit of oil that'll drip out then set them in the morning.

Also, Kurt's tip on adjusting the mixture screw 1/8 turn CCW worked well for me. Once your timing is set, it's probably good for a long time. 1980, hmm...may be the year they switched to electronic ignition. I don't think you have points, do you? Another thing you might want to consider is removing the emissions gear for about $12, a kit from most dealers can help it breathe easier and run a little cooler. Now that its a 'classic', its legal in my state anyway. Might want to check yours first.

Got pics of the bike? :dunno