Author Topic: My first signs of middle age and some BMW questions (Read 3458 times)

tsflstb · « **on:** May 12, 2008, 09:19:25 PM »

Bought my first "old man's bike". Never thought I'd consider anything with all that useless stuff like mirrors, horns, upright bars, comfortable seat, headlights that are bright, centerstands etc... But I found a Cragislist ad for this '84 R80RT at a good price.

It's a definite change of pace from my 400F and I'm pretty impressed. I like the relaxed gallop of the twin instead of the 400's scream sometimes. It's still pretty light on its feet for a "touring" bike. I'm seriously considering riding it up to Indy for the GP races in September - about 2500 miles round trip.

I discovered the dented, faded tank on the 400 is actually BMW orange now.

It needed a couple of things. I've gone through the brakes. I guess they use some kind of ceramic or phenolic pistons and bores - so no corrosion - nice. It stops better now, but I'm going to get steel lines eventually.

I also gave the carbs a cleaning but have a question there. It starts fine, idles fine when warming up but after a few minutes of riding the idle doesn't always return to where it should. It will hang up at 3K RPM sometimes. Acts like an air leak but I can't find any. It's also intermittent, so I'm not sure what that means. When I re-installed the carbs, I realized there's no real way to know how to orient them to the engine. How critical is "level" for one of those Bing carbs - meaning do I need to have them perfectly vertical? Am I screwing up the float level by being off a little?

It may also just need a carb synch since I messed with them, but I thought I'd ask the stupid question about the carb position first.

DarkRider · « **Reply #1 on:** May 13, 2008, 01:33:35 AM »

Nice bike man...seems like a nice middle ground when you dont want your arm sockets yanked out by the FZR and dont want to be deafened by the CB.

Roach Carver · « **Reply #2 on:** May 13, 2008, 01:25:34 PM »

I have a 72 r75/5. Bing carbs. I remember in the manual something being said about the carbs orientation to vertical or something. as far as causing an idle problem, I am not sure. could it be a pinched cable? I would also make sure that the boots are not leaking.

colb · « **Reply #3 on:** May 13, 2008, 01:44:32 PM »

http://www.motobins.co.uk/yabbse/index.php
Good source of info for what you are looking for, UK site and the guys on this forum are a great bunch.
Sign up and get your answers

tsflstb · « **Reply #4 on:** May 13, 2008, 06:50:47 PM »

Thanks for the replies. There are some good BMW forums out there...I just need to start searching them I guess. Don't want to come off as the village idiot on my first post. I have both clymer and haynes manuals but I didn't see anything about it. I think just eyeballing the carbs' vertical would be close enough, but I'll do the research.

I need to triple check for air leaks and may change out the carb diaphragms and all the o-rings since I have a couple of rebuild kits anyway.

I'm really enjoying the bike more than I thought. The FZR and 400F are toys - fun but it's obvious I'm just out screwing around when I'm riding. This BMW is "brutally practical". I just picked up two gallons of milk, some diapers and a loaf of bread - and had fun doing it. Having young kids keeps me on a short leash most of the time. I'll get a lot more riding in now that I can make grocery runs and go pick up items that we "need" across town.

bryanj · « **Reply #5 on:** May 14, 2008, 09:31:43 AM »

The thing i remember about BM's ithat they dont come top in any category but they come 2nd in all of them

Tom in Newcastle......Ontario · « **Reply #6 on:** May 14, 2008, 09:57:06 AM »

I,ve had my 84 R80rt for 3 years now,has 92,000K's on it(55,000 miles)I have to admit I love the fairings and bags,full face helmet fits in and the lid closes,yes quite agile,not bad on twisties not bad on back roads (with-in reason)not bad on fuel,my butt does get a bit sore on it but after 2-3 hours ,not too much to really complain about,the upright riding position is nice ,,,,,and what's really nice,you don't see too many of them on the road,

mine runs a bit rough before warm-up and then runs well,idles a little higher when warm but not much..

fuzzybutt · « **Reply #7 on:** May 16, 2008, 11:32:33 AM »

level is REALLY critical on those bing carbs, also chec kto be sure the throttle cable is seating properly in the bracket on the carb.

DarkRider · « **Reply #8 on:** May 16, 2008, 12:58:23 PM »

Just a thought...the 400 would look great in that color! On a side note after reading about the different beemers on this site im seriously pondering one as well now especially after doing some looking and finding that they are quite affordable for the older machines...I may just have myself a beemer before i get a Blackbird..

tsflstb · « **Reply #9 on:** May 16, 2008, 09:08:48 PM »

I need to pull the carbs again this weekend and see what's going on. I'll replace anything that can leak in there and check the float levels again.

Is there a way to check the level of the carb body itself? I've just got the clymer and haynes manuals and they don't mention anything. Should I put my torpedo level on top of the carb to level it perpendicular to the engine?

I noticed today that when I get on the brakes hard the engine races up to 4K RPM. Pretty sure I'm not touching the throttle when that happens. There's a lot of fork dive, so I wonder if fuel is sloshing forward in the carbs' float bowls when that happens? I'm going to put some extra slop in the throttle cables and see if that changes anything too. Maybe they are getting kinked.

Other than the carb issues, I'm loving this thing. Blackbirds are nice but for day to day commuting this is the ticket. Not the fastest or most exciting bike but it's built solid and pulls like a tractor.

ofreen · « **Reply #10 on:** May 16, 2008, 09:41:29 PM »

The R80 is a great bike, usually smoother than the R100. You might check this place out if you haven't already.

http://www.airheads.org/

tsflstb · « **Reply #11 on:** May 16, 2008, 10:06:32 PM »

Thanks, yeah I've sent my request to subscribe to their email list. Looks like a pretty active group.

ofreen · « **Reply #12 on:** May 16, 2008, 10:52:26 PM »

yes it is

fuzzybutt · « **Reply #13 on:** May 17, 2008, 11:44:00 AM »

not too many motorcycles more reliable and durable than an airhead. my instructor at AMI has one with almost 200k miles on his.

Uncle Ernie · « **Reply #14 on:** May 21, 2008, 04:51:44 PM »

Sorry I don't get to the "Other Bike" Dept too often...

I'm not terribly familiar with that particular year, but first check to make sure the diaphram isn't cracked.
Mostly, it sounds to me like the automatic advance is hanging up. If it's the style I think it is, there are 2 weights in a coffee can type of contraption that are spring-loaded. When they don't contract all the way, the revs stay up. Total PITA to fix. The easiest solution is to drag the revs down by not pulling in the clutch until the last second at stops. You get used to it- (I did

)

tsflstb · « **Reply #15 on:** May 21, 2008, 09:56:29 PM »

This has electronic ignition with the mechanical advance. I'll add that check to my list of 'to do's'

It appears very easy to service according to Clymers - "remove and take advance unit to authorized BMW dealer for service". Asshats.

I've got high-temp silicone curing on some very superficial looking cracks on the intake boots, new carb diaphragms even though the old ones looked fine (didn't help). New o-rings on the air screws (didn't help), and I'll check the valves when mr. liquid wrench finally works the right spark plug loose. I can barely turn the engine with the rear tire when the compression stroke hits, so I'm going to assume compression is good for now.

After that I'll hook up the Carbtune, synch them and hope for the best.

I'm reading about the "valve recession" problems that seem to be the only weakness on these bikes (up to '84). I don't think my symptoms relate to that but I'll monitor valve clearances closely since it's easy to do.

tsflstb · « **Reply #16 on:** May 25, 2008, 09:31:44 PM »

Crap.

Any chance of getting the remnants of this sparkplug out without removing the head? It's still soaking in PB Blaster - mixed with some of my tears now.

ofreen · « **Reply #17 on:** May 25, 2008, 11:22:53 PM »

I hate it when that happens. If you have to take it off, the head comes off easily, except your next challenge may be the exhaust nut. If the sparkplug was stuck in there that bad, it is likely nobody has periodically loosened the exhaust nut and anti-siezed it. Those threads for the exhaust nut on the head are fine and easily damaged, so use some care. If the nut won't come off with heat and PB, split it, and get a new one. They are cheap.

Hopefully, somebody didn't crossthread the sparkplug in there for you.

tsflstb · « **Reply #18 on:** May 26, 2008, 07:16:51 PM »

Thanks. I got all the porcelain part of the plug out now. I just have the threads and electrode left in the head.

Still soaking it and hitting it with the heat gun once in a while. I'm going to do that for a few more days before I try an E-Z out. Never done it before, but I have the square section type that you hammer in and back out. I guess it just depends on how "stuck" it really is.

ofreen · « **Reply #19 on:** May 26, 2008, 07:39:40 PM »

Good luck.

bryanj · « **Reply #20 on:** May 27, 2008, 01:54:50 AM »

Forget the easy out either get the helicoil kit or take the bike to a shop that does Helicoils for plugs, make sure they grease all the tools well to catch shavings and start it on one cyl with the plug out to blow any other crap out

tsflstb · « **Reply #21 on:** July 25, 2008, 11:34:39 AM »

Pretty sure nobody is losing sleep over this, but it's Friday at work...I've put a few hundred miles on the bike now and think *knock wood* that it's sorted out.

Ended up removing the head and having a helicoil installed for the spark plug. I have one of those nifty BMW exhaust nut tools now. I put everything back together with a heapin' helpin' of anti-seize.

I scratched my head when checking the valve clearances because there weren't any. My feeler gauges don't read negative numbers, so I'm not sure how tight the exhaust valves had gotten. Anyway, set them to .008" and synched the carbs and its runs and idles like it should now. I get a small backfire from the left side once in a while, so I'll probably put the Carbtune on them again for some fine adjustment.

I'm going to check the valves again soon to monitor the gap. Hopefully the valve seats are settled in and done moving around. Doing my research after buying the bike, I learned this is a common problem on pre-'85 models.

Anyway, I'm getting a good crash course in German bike maintenance. Next I'm going to tackle changing the differential fluid and lubing the clutch splines, whatever the hell those are.

tsflstb · « **Reply #22 on:** July 25, 2008, 11:49:58 AM »

Forgot to ask - the valves didn't look burned, but is there another way to tell if they got too hot by being tight? It seems to have good power and compression, but I guess they could have been weakened by the heat too. The bike had 30,000 miles - not sure when or if the valves were ever checked before.

ofreen · « **Reply #23 on:** July 25, 2008, 01:16:44 PM »

Quote from: tsflstb on July 25, 2008, 11:34:39 AM

I'm going to check the valves again soon to monitor the gap. Hopefully the valve seats are settled in and done moving around. Doing my research after buying the bike, I learned this is a common problem on pre-'85 models.

Anyway, I'm getting a good crash course in German bike maintenance. Next I'm going to tackle changing the differential fluid and lubing the clutch splines, whatever the hell those are.

Good plan on keeping an eye on tappet clearances to see if there is the valve recession problem.

Here is a link for doing the spline lube by the famous Snobum.

http://www.airheads.org/content/view/209/98/

Don't be put off by all the steps in the process. Give yourself plenty of time and its not hard. It will seem like you have half the bike apart before you are done. Be comforted by the fact that the second time will go a lot quicker. If you don't when (or if) the last time the spline lube was done, I wouldn't put it off. It is a little expensive if those splines wear out and fail. You give it some gas someday, and instead of forward motion, you get interesting noises.

As for the lube to use, check and see what BMW recommends these days. Their recommendation changes periodically. They will sell you a little tube of the stuff that will last you a long time, since you don't use a lot. In fact, you don't want to overdo it, as the excess flies off and contaminates the clutch plate.

Have fun.

Edit to add - Just noticed my 1000th post on the SOHC4 site is about beemers.

tsflstb · « **Reply #24 on:** July 25, 2008, 09:36:08 PM »

Thanks for that link. I've saved it for future reference. That guy is nothing if not thorough in his instructions.

The BMW Airheads site is like drinking from a fire hose. I tried to keep up with the mailing list for about a week - wow. I do search the archives now and usually find what I need there. It's a great resource, but the advice here is usually on the money too.

Oh - congrats on number 1,000 Ofreen. It was a keeper for me.

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Author Topic: My first signs of middle age and some BMW questions (Read 3458 times)

fuzzybutt

fuzzybutt