R60/6 '75 backfiring issues.

Discuss all things 1970 & later Airheads right here.
User avatar
Lasse
Posts: 30
Joined: Tue Aug 03, 2010 12:32 am

R60/6 '75 backfiring issues.

Post by Lasse »

Hi guys this is an "update" originally written for advrider, but maybe you have some pointers too? :)

It's an R60/6 with /5 carbs, I have owned her for two days now. First airhead.

I went to the parkinglot to start her up. She was backfiring alot and as yesterday it was hard to get her going. I am getting fire out of the LHS pipe. With alot of backfiring I reached my garage. Pulled the plugs LHS (Blue header, fire, struggling side) was black. RHS was whiter/greyish. Gap was a tad over a nails thickness. So OK.

Image

Mixturescrews a set different, I guess this is down to them being in sync. Well, hopefully in sync.

Image
LHS

Image
RHS

Pulled the carburettors(/5 carbs), nothing to see, floatbowl chambers were clean. A bit "gunk" between the brass insert and the carburettor body, nothing that would harm anything. Cleaned it out, blew out all jets. No change.

Image

Pulled generatorcover, pinched wire. Thought that could have an effect, so I made sure it wouldn't touch metal to short out. No change.

Started her up and had my hand on the throttle, applying a little pressure, it was bogging and struggling. Removed my hand and it putted along nicely, albeit some hesitations from the LHS side again. Put both my hands behind the pipes to feel the pressure. LHS as struggling, RHS side was even and felt as should be. Switched the plugs around, both sides even now, might have been because the engine got a bit warmer, don't know.

I put it all back together and headed home, it was "surging", by that I mean that it would sometimes pull stronger some of the way up through the rev range. Got home, listened to the valve train. LHS side SEEMS louder than the RHS side.

So next up is that I want to confirm a correct timing and then set the valves. And also try to switch around the HT leads.
User avatar
Lasse
Posts: 30
Joined: Tue Aug 03, 2010 12:32 am

Re: R60/6 '75 backfiring issues.

Post by Lasse »

I did a little video for you to see:

http://www.youtube.com/watch?v=FRNEnOCXMj8
Deleted User 72

Re: R60/6 '75 backfiring issues.

Post by Deleted User 72 »

R60/5s are delivered with a different carb than the 750/5s. Never having had a 60/5, I don't know ALL the differences, but running a carb meant for more displacement than you have is going to involve trial and error experimentation to find the "correct" jet/needle combination. All I can tell you is you're likely going to have to go leaner with jets etc. to find a happy combo. "How much leaner" will have to be answered by smarter wrenches than me.

GSPD is a likely candidate for this issue but he ain't shown up here, yet.
User avatar
Lasse
Posts: 30
Joined: Tue Aug 03, 2010 12:32 am

Re: R60/6 '75 backfiring issues.

Post by Lasse »

Why would this be carburettors for a R75? I am confused now. The bike is an R60/6 with /5 carburettors I am told.

It has been running good with this setup.
Kurt in S.A.
Posts: 1583
Joined: Tue Aug 03, 2010 12:08 pm

Re: R60/6 '75 backfiring issues.

Post by Kurt in S.A. »

You'll have to be specific when you say /5 carbs...please supply the carb number. The R50/5 and R60/5 came with slide carbs; the R75/5 came with CV carbs. The specs indicate that the R60/6 also came with slide carbs, so there might be a reasonable match up. Actually, it appears that the R60/5 and R60/6 had identical carb numbers. The Bing book shows carbs 123/124 were used for the R60/5 and R60/6. The book also shows carbs 111/112 were used on the R60/5 only. These should be Type 53 carbs.

From the wee look at one of your photos, it looks like you have slide carbs

Kurt in S.A.
User avatar
Lasse
Posts: 30
Joined: Tue Aug 03, 2010 12:32 am

Re: R60/6 '75 backfiring issues.

Post by Lasse »

I do have slide carbs, matching, as in two LHS carbs I think. The tickler is on the same side atleast.
The bike has been running with this setup for years prior to me buying the bike two days ago.
Major Softie
Posts: 8900
Joined: Tue Aug 03, 2010 1:46 pm

Re: R60/6 '75 backfiring issues.

Post by Major Softie »

Okay, so what are the purchase circumstances here exactly?

You bought this two days ago and it's running like crap, but you know it's been working fine for years. How do you know this? Is this what you've been "told," or have you been around the bike for those years and know that it worked fine up until virtually the moment you bought it?

In other words, we need to know if it's more likely that you've been lied to, or if this is just an amazingly bad luck coincidence.
MS - out
User avatar
Lasse
Posts: 30
Joined: Tue Aug 03, 2010 12:32 am

Re: R60/6 '75 backfiring issues.

Post by Lasse »

Because I rode it home for 232kms without any issues. I have spoken to the guy who did the rebuild (Not the one whom I bought it from) , and it has been running solid.

And the problems have got worse it seems, over these two days. I'm thinking a burned valve now. But its too early to tell.
User avatar
Lasse
Posts: 30
Joined: Tue Aug 03, 2010 12:32 am

Re: R60/6 '75 backfiring issues.

Post by Lasse »

Today I wanted to get the seat and tank off so I could do a visual inspection of coils and so on.

Well I failed at taking off the seat, I can't figure it out.
Image

Took of the rear hinge and then pulled the seat out of the front hinge, but I couldn't find a way to get it free of the subframe. The front hinge is riveted.

Checked for wires that had been chewed in, but there wasn't any to see.
Image

Switched the leads around on the coils to see if there were any changes in the sound of the engine. No change.

Checked the mixturescrews, LHS was 3/4th of a turn out RHS was 1,5 turn out. I screwed them as far in as possible and ½ a turn out. I don't really know if that changed anything, though both sides finally seemed to be heating up together. As it made no change, I put them back as they were.
Deleted User 72

Re: R60/6 '75 backfiring issues.

Post by Deleted User 72 »

Lasse wrote:Why would this be carburettors for a R75? I am confused now. The bike is an R60/6 with /5 carburettors I am told.

It has been running good with this setup.
Sorry, Lasse. My mistake. I read /5 carbs and immediately thought of the only /5 experience I have which is with my own R75/5.
Post Reply