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Not convinced it’s running right…

The place to discuss the R 90 S as well as the R90S Worldnet archives!
Workinman
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Re: Not convinced it’s running right…

Post by Workinman »

Okay, guys. I finally got new tires mounted, and I rebuilt both calipers, and the master cylinder, and installed new braided lines and new pads. So after that stuff was done, I got to take her out and ride up and down my dead end street. This puppy is running REALLY bad! It fires up fine, and idles fine, but try to actually make it move and it’s a whole nuther world. It still acts like it’s running on one cylinder, even though both cylinders are getting hot. I did a compression check today after my short ride and I got 130 on the left cylinder, and 135 on the right. The left plug is a little darker than the right, but neither is “wet”, as in unturned fuel or oil.
So here’s what I’m thinking. Please keep in mind this is the first time I have EVER worked on an airhead. I’m used to flat fours, inline fours, etc with Mikuni carbs. The boxer and the Dellortos are French to me. But I’m thinking that I want to pull off the air intakes from the back of the carbs and glance in there and look at the accelerator pumps to make sure they are working.
Then I want to check valve clearance and timing. I’m assuming there is a bolt or nut or something on the front of the engine to turn it over with? Clockwise or counterclockwise clockwise? Timing light hooked to left cylinder or right cylinder? Points set to .016?
Thanks for any and all help you can give. Everything on this bike is foreign to me at this point. I’m learning, but I’ve got a long way to go. And I can tell you that the way it’s running now ain’t gonna work! I couldn’t even make it up the moderately steep hill at the end of my road. Had to stop and turn around. Now THAT is sad.
Thanks again!
Chris

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schrader7032
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Re: Not convinced it’s running right…

Post by schrader7032 »

Turning engine: put it in 4th or 5th gear and turn the engine using the rear wheel. If you pull the spark plugs, it will turn easier. Valve covers off, straddle the rear of the bike and pull the wheel around in the forward direction. Watch the left intake valve. When it opens, and then closes, reposition yourself on the left side of the bike to look into the case timing hole. Bump the rear wheel around, watching for the OT mark. When it shows up, then you can adjust the left valve clearances. 0.15mm intake, 0.2mm exhaust. Rotate the engine 360 degrees, or watch the right intake valve for opening, closing, then you'll know you're approach OT on the right side.

Timing light: can be hooked to either plug wire...both cylinders fire at the same time. You should see only one S mark. If you see double images, it could indicate a timing differential with the cylinders reaching their firing point at a slightly different time. If the distance between the two images is less than 0.25", it's OK. More than that, might take some "adjustments".

Points gap: nominally 0.016" is used, but the gap can be a wide range and still run OK. Set it at 0.016" and see where you are. Ideally, you would then adjust the entire ignition backing plate to bring the timing into the window. But if you turn the plate and it runs out of travel, don't hog out the holes in the plate, just go back and tweak the gap. A small gap change can make a big difference in timing.
Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2
Fast. Neat. Average. Friendly. Good. Good.

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srankin
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Re: Not convinced it’s running right…

Post by srankin »

One of the fellows who contributes regularly to the BMWMOA forum is Brook Reams. https://brook.reams.me

While he is not covering a R90S, some of the videos and information will cross over for your bike and may prove useful to you in learning the ins and outs of the bike.

Boxer2Valve is selling downloadable videos for a R90/6, again, it is not exactly the same as your bike but the basics are the same. https://www.boxer2valve.com/service-vid ... rials.html. I have not viewed any of this video series but have watched others and they are also well done.

Both sites beat the heck out of how I learned to do stuff on my bikes, Chilton's, Hayes, and factory manuals were the thing. The internet has opened new doors for learning, sometimes LOL, depends on the teacher. These guys are good. St.
Owner of a 84, R80RT and 78, R100RS

Workinman
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Re: Not convinced it’s running right…

Post by Workinman »

So get this…
I went back out to the garage and pulled the left intake tube off. I wanted to look in there and see what was going on with the accelerator pumps. I twisted the throttle and NOTHING happened. The right hand slide went up, but the left slide just sat there looking stupid. It had come off of the cable. That explains why the temperatures were the same at idle. Both cylinders were idling just fine. Anything over idle and the left cylinder wasn’t pulling his share of the load.
Anyway, fixed that problem and it’s like having a whole different engine! What a sweetheart! I haven’t ridden it yet because I still want to check the valves and the timing first, but I can tell you that I’ve found the problem!
With that being said, I’m still not happy when I open the throttle any faster than a snail. It bogs. I remember reading somewhere, possibly on here, and possibly on Snowbums site, (That man is incredible!) that when you reassemble these carbs you must be very careful how you put the pumps back in and you have to prime them or they won’t work. That’s something I have to check out also. Has anybody heard of this? And by ANYBODY, I mean either of you.
Thanks again, and I’m going to go back and reread your last responses.
Chris

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srankin
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Re: Not convinced it’s running right…

Post by srankin »

Ah I love it when things get taken care of and improve. Good catch on your part. Sadly, I never messed much with Delortos as I never really had my R90S bikes running much longer than bench tests. St.
Owner of a 84, R80RT and 78, R100RS

Workinman
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Re: Not convinced it’s running right…

Post by Workinman »

Todays update. Actually yesterdays update.
The bike was bogging pretty bad! Enough that I KNEW there was a serious problem that I had to figure out. So, this time I pulled the intake tube off of the right side, saw nothing causing a problem, so I pulled the slide out of the right carburetor. Sure enough, the clip holding the needle in position wasn’t holding the needle in position, so it was just floating around in there doing whatever it wanted. Ive ordered new clips for both sides as these seem kind of weak after 48 years. For now it’s holding the needle just fine, so I’ll be okay for a week or so waiting for the clips.
Took the bike out for the first time, other than up my short road and back, and went for a 17 mile ride. I wanted to at least try it as it’s supposed to rain for the next three days and I knew I wouldn’t get a chance. The bike ran like a TOP. Everything worked pretty much flawlessly, with the exception of the speedometer needle. It was flopping around all over the place! It would go from 30 to 120 and everything in between. I’m going to pull the speedometer cable off and check it. Hopefully it’s just that and it will be an easy fix. If not, we will do whatever we gotta do to get it working better than that. My GoldWing speedo is off by about 10 MPH, but it’s steady and it’s rather consistent, so I can deal with that. This thing is all over the place!
Oh, and the timing was also off. When I hooked my light to it, before making any adjustments at all, it was sparking just before the OT mark on the flywheel. I set it back to spark at the S mark, and everything seems fine now.
Today is valve adjustment day, rocker arm end play adjustment day, speedometer cable checking day, and oil leak finding day. I think my push rod tubes are weeping. Is this a relatively easy fix or do the heads have to come off? I haven’t checked into that yet.
Once again, I thank you guys for your guidance in getting this thing roadworthy. I see a lot of good riding ahead of me with this bike. It won’t replace my R1200RT, but it will certainly be an entertaining alternative.

Werner1111
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Re: Not convinced it’s running right…

Post by Werner1111 »

Great news and great troubleshooting. Srankin was on it from the beginning regarding the carbies. Enjoy your 1st airhead. It's a special bike.
R69 R90/6 R100/7 R100S R1150GSA S2R1000

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srankin
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Re: Not convinced it’s running right…

Post by srankin »

Nice to read your progress. Hopefully the speedo cable is the only thing whacked up. IF you need to have a speedo repaired, I would suggest staying away from Palo Alto, very expensive and I have a friend who is an ongoing dispute over a tachometer repair he sent them. My own experience with them is bad because I called, and asked a price and was quoted a sky high number. Overseas is more customer friendly. There is a fellow; Terry Vrla terryvrla@hotmail.com

Unfortunately to change the push rod seals, the rocker arms do have to come off, however, you do not have to mess with taking the heads or jugs off, they will slide on the four bolts far enough the rings are not disturbed, the head gasket is not disturbed. There is just enough to wiggle new seals in.
LOL, you don't even have to take the carbs off the cables, just unhook them from the head and let them dangle, no, seriously get a strap to hold them out of the way while you work.

Good luck, St.
Owner of a 84, R80RT and 78, R100RS

Workinman
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Re: Not convinced it’s running right…

Post by Workinman »

Thanks. I’ve looked at videos about changing the pushrod tube seals, and I may just go ahead and pull the jugs and all off. They need a paint job! Still thinking about that, as I can still ride it the way it is, and that sounds like a winter project to me.
The speedo cable is weird. I pulled it loose at the transmission and hooked the cable up to my cordless drill. (In reverse) The speedo seemed to work just fine. It went up to around 10-12 MPH on low speed, and around 68 or so on high speed, and just sat there as pretty as you please. That tells me that the cable AND the speedometer are working fine. Once again, this is gonna take some trouble shooting.
I did get the valves adjusted today, and the rocker arm free play, and retorqued the heads, so if it ever stops raining, my butt is headed up into the mountains for a GOOD shakedown cruise. I will let you guys know how it goes.

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srankin
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Re: Not convinced it’s running right…

Post by srankin »

There is not much involved with the gear drive system for the speedometer, at least nothing to wear out in the trans, the gear in the trans driving that end of the cable is metal. LOL Frankly, I would make sure the cable is seated properly into position on the transmission and give it another try on the road. Same goes with the cable end at the Speedometer.

You can get a decent cable from EME for about $50, so second, I would replace the cable. If that fails, the problem will be in the speedometer itself. LOL, if you get a new cable, you will have one more new part, if the old cable is still good, keep it for a spare or reuse it later. St.
Owner of a 84, R80RT and 78, R100RS

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