Topic: 76 550 runs best with out air filter.......hmmmmmm

[Bluto]

bought this ole gal brand new in 76.  Rode er for a few years back then....stored her well..... and just got her back on the road last year. Had the carbs cleaned and put a new 4 into 1 on her to replace the old 4 into 1 that had rusted out.. The only prob is that with the NOS paper filter element I get a serious sputter up in the high rpm range.  At about 7000 it just won't go any higher.  I tried a foam element and it was worse.  With no air filter at all.......runs like brand new.

Now I figure running without a filter will cost me sooner or later.  Last thing I wanna do is take them d#m carbs off again!!!

Could I possibly help this with fuel/air screw adjustments?  Far as I know all the jet sizes are stock.

Thanks,

Bill

[TwoTired]

The air bleed screw has little effect at throttle positions above 1/4.

Need to know if the emulsion tubes are clean, if your main jets have been modified, and what position the slide needles clips were placed in.

Wouldn't hurt to remove the spark plugs and note what numbers are on them and what the deposits look like on the center electrode insulator.

Naturally, all the other items on the tune up check list should be addressed/confirmed before mucking about with carb mixture adjustments.

[Bluto]

The air bleed screw has little effect at throttle positions above 1/4.

Need to know if the emulsion tubes are clean, if your main jets have been modified, and what position the slide needles clips were placed in.

Wouldn't hurt to remove the spark plugs and note what numbers are on them and what the deposits look like on the center electrode insulator.

Naturally, all the other items on the tune up check list should be addressed/confirmed before mucking about with carb mixture adjustments.

Back when I bought it new I had a bike shop take the stock exhaust off ( I know....I would love to have them stashed away..what can I say...I was 17 ) and they installed 4 into 1 pipes.  As far as I know they did not change the jetting.  In fact I did get a re-build kit for 1 of the carbs and the jet numbers are the same and the kit was for factory specs.

Never looked at the needle clips.  Is that as simple as taking the tops off the carbs?  And is that simple?

As for the plugs that is likley an issue.  When I tried to take them out they were WAY stubborn and after getting them all to turn a bit...I just torqued them back down.  I was very afraid of stripping the housing...so ...yep.  I am running 33 year old spark plugs. 

Got any ideas on how to get them out without damaging the threads?  Like I said...It runs like a dream without an air filter.  I'd hate to blow it trying to get new plugs in it.    Thanks for the help,

Bill

[bistromath]

Well, sooner or later you're going to have to get those plugs out, so you might as well get on them. Hit them with PB Blaster or another penetrating oil (although PB is the best), and wait a day or two. Then when the engine is cold, wrench them out. Never heard of someone stripping threads getting the plugs OUT, unless they were super overtorqued going in. Usually people strip threads overtightening the plugs when they put them in.

Sounds like you're running rich: if you remove the air filter, more air gets through, leaning out the mixture. Do you hit this 7000RPM "wall" at 1/4 throttle? 1/2? 3/4? WOT? This will tell you where the problem in your jetting is. If you hit the wall at WOT, your main jet is too large. If you hit the wall at 1/4-3/4, your needle clip is too high. Doing a "plug chop" (search the archives for loads of threads about this) will give you a more definite answer. On the other hand, if it was running like a dream when you put it away, I'd look at cleaning the carbs, especially the float levels.

First thing though, give the bike a tune-up: plugs, adjust cam chain, adjust valve lash, adjust timing. Then give your mixture problems a look.

[TwoTired]

As far as I know they did not change the jetting. 

And, as far as we know the bike is running fine...
Knowledge is power.  It's usually what you don't know that creates a headache.  FYI, it shouldn't have been necessary to change the jetting.  Bt, the only data we have is that the carbs were dismantled and put back together by someone who may or may not have changed the internal components.  We recently had a thread where some previous "mechanic" changed the mains from #100 to #68.  No one knows why, but the engine had no top end and putting the factory parts back into the carb returned the bike to fun status.

In fact I did get a re-build kit for 1 of the carbs and the jet numbers are the same and the kit was for factory specs.

There are several threads where run problems have been corrected by changing the carb internals BACK to stock components, particularly the slide needles and the emulsion tubes.  Aftermarket parts are often cheaper because the parts aren't made to precision standards or the quality control measures were bypassed.

Never looked at the needle clips.  Is that as simple as taking the tops off the carbs?  And is that simple?

Dunno about you.  It's simple for me.  But then, other people do things simple for them and hard for me.  The needles can be checked/ changed with the carbs on the bike.  Yes the tops come off, the actuating arm bolt removed, the internal linkage dismantled, the two screws on the slide tops are removed, and the slide can be extracted.  After everything is put back together, the carbs need to be vacuum synchronized.  Does this sound simple to you?

As for the plugs that is likley an issue.  When I tried to take them out they were WAY stubborn and after getting them all to turn a bit...I just torqued them back down.  I was very afraid of stripping the housing...so ...yep.  I am running 33 year old spark plugs. 

I don't think it is reasonable to expect top performance out of old spark plugs where you can't even determine their condition.  If their is spooge on the threads, their is a risk of damaging the threads in the aluminum, particularly if burnt oil has glued the plug to the threads in the head.   You should certainly have the proper tool for the spark plugs, such as the one that came in the original tool kit.  It is fairly easy to cross thread the #2 & #3 spark plug holes upon installation if you don't.

Got any ideas on how to get them out without damaging the threads?

Remove them with the head hot?  Or, at least loosen them so penetrating oil can seep into the threads.  Some time ago, I posted a recipe for 50/50 acetone and auto trans fluid as a very good penetrating oil, outperforming some highly touted products for that task on the open market.

Like I said...It runs like a dream without an air filter. 

Your call.  You COULD simply run it like that until the injested dust blasts the cylinder walls, the rings wear out, and blowby dust contamination in the oil supply takes out the bearings.  Replacement used engines are fairly cheap if you shop around.  Or you could simply toss the bike aside for another.  It been done that way before.

Personally, I'd rather have my bike working as it should.  But, that's just me and my quirks.

Cheers,

[Bluto]

Of course you are right twotired.  I've gotta keep the old girl running.  Too much sentimental value there.  Gotta love all those little dobs of yellow paint on all the bolts.

I'm running with the paper air filter now (rode 150 miles today......had a blast.) and she ran good.  Only a slight sputter under very heavy acceleration (which I have no business doin anyway).

I'm gonna tackle those plugs after the summer and see what gives.

Thanks for the input!!!!

Bill

[fondofhondas]

I use a product called "deep creep" its made by the "sea foam" manufacturers. all their stuff is amazing. pb blaster is great, but deep creep cleans parts wile it penetrates. along with 100 other uses.