Stuck in high rpm

So I'm here trying to get the beast ridable to take her about 2 miles down the road to have her carb tuned. But I have this problem. See I'll start her and the rpm will jump to 3-4k and hang for a sec then seems to go higher slowly so I'll kill it. Restart and sometimes it'll just go to idle speed and run fine...UNTIL I rev the engine pretty decent and it'll jump to 3-4k and try to go higher with out dropping so I kill the engine. Why is this happening? Carb just basic bench sync. Mix screws 1 turn out. throttle cable and choke not hanging. Everything appears operational. Remember I just need to take it on a short ride to get her fixed any ideas?

 

We need a bit more information. What else was done when you had the carbs off? Full rebuild? Butterfly shaft seals?

When you initially start the engine, I assumed you have it choked, correct? What happens if you slowly reduce the amount of choke? My turbo will do the same thing and rev to 4500 if I let it go on fully enriched(choked) but I move the enrichener lever back a bit till it's turning over about 1800 or so till it warms up.

If your engine is warm and it's still screaming, you either need to reach under the bank of carbs and reduce the idle speed or you either missed something during reassembly or you bent the throttle shaft when you removed/attempted to remove the butterflys but we really need more info as this is taking guesses by not knowing the whole story. Anything can be fixed, no matter how bad it is but no one will be able to help you till we hear the rest of the story....


jeff

 

Back to basics for a second: HAVE YOU CHECKED THE VALVE CLEARANCES???

If not, then you (or anyone else for that matter who knows what he's doing) is NOT going to be able to get a good vacuum sync.

Your problem is likely 1: Float levels; or 2: you're WAAYYY out of sync. If you get "way out of sync" symptoms with a good solid bench sync it's another clue that you need to check the valves.

Have you checked and set the float levels? How?

 

Float levels checked with clear tubing. Set a fuel supply above carb on bench on pri. All float bowls open and used clear tubes to check levels. All levels are the same across the board.

 

You didn't answer my first, and the most important, question.

But now I have yet another;

since the float levels are good, what method exactly did you use to "bench" sync?

Remember though, like I said, neither you or a shop will get a good vacuum sync until the valves are in spec.

 

Ok I think I'll redo the bench sync with a old card. I am also going to order the yics and colortune from len. It will cost less for the tools than to shop it. Today while checking valve clearance one was perfect all the others I couldn't get my feeler under the lobe. Bike was warm and the shims could easily be moved with my finger. Should I still check this when the bike is totally cooled down? The floats are perfect. Today I was having some non firing pistons. I am thinking of buying a new set of plugs. How do I check to see if my plug wires are good? I am determined now.

 

In the future, don't use a REAL Feeler Gauge to Bench Sync.

Use something that will conform very-easily to the Convex Curve without binding.

Thin strips of:

3X5 Card
Business Card
Resume' Paper

 

Ok I think I'll redo the bench sync with a old card. I am also going to order the yics and colortune from len. It will cost less for the tools than to shop it. Today while checking valve clearance one was perfect all the others I couldn't get my feeler under the lobe. Bike was warm and the shims could easily be moved with my finger. Should I still check this when the bike is totally cooled down? The floats are perfect. Today I was having some non firing pistons. I am thinking of buying a new set of plugs. How do I check to see if my plug wires are good? I am determined now.

 

auto:

If I was as psyched as you, ... to want to get the Bike to where all you need to do is stick the keys in it ... fire-up and roll.

This is what I'd do:

Solder-in a Brand New Fuse Panel
Replace the Coils and Spark Plug Wires with Performance Parts
(Dyna or Accel)

Yank-out the Gremlins and live - life - large.

 

Ooh, zero clearance=bad.

Yes, you need to check the clearances cold. But if it was cooled down enough for you to touch it without burning yourself, and you couldn't get feeler gauges under the lobes, you've got some really tight valves (no surprise at 20K if never touched.)

You should be able to move the shims (and buckets) around easily if the cam lobe isn't pressing on them.

GET THOSE VALVES IN SPEC before you burn a couple (if it's not already too late.)

THEN get the carbs sync'ed. You won't be able to with 7 tight valves anyway.

Now do you see why the book (it's not just me) says to get the valves in spec first? We don't just make this stuff up...

 

I know I know I have the book now. I'm going to check them vavles today and see where theyt stand. Getting them out looks quite tricky I'll see if the clearance is good if not I'll pull them and I'll post the results.

 

Ok just got done trying to check valve clearance. Found I couldn't get my feeler under any no matter where I pointed the lobe. So now what do I do?

 

Also discovered my firing problem. Bad plug wires yay me.

 

Can I put off the valves till wintertime?

 

NO !! You can't get a 0.004 inch feeler gauge under any??
The engine ran?? Something's wrong with your technique, I think.
Or the valves are really tight !!

 

OR they're close to dead tight. At that mileage it's very possible, more like probable. I had seven too tight at 7100 miles. It'll run, but like crap and have a hard time idling once warm.

What you'll need to do is extract the dead-tight shims, read them, install a couple sizes thinner ones and re-check the clearances; then you will be able to "adjust" them further based on the new, "true" reading.

I have a small collection of used shims that I've been known to loan out for just such troubleshooting.

And TIME is right; NO, you absolutely cannot put the valves off if they're that tight. You may have already begun to "burn" a couple of the exhaust valves; do you want to do a basic maintenance procedure or a full-on, pull the head and spend money valve job???

PM me if you need to borrow some used shims.

And quit riding the bike until you get the valves remedied, or you may do actual damage (if you haven't already.) Honest.

 

OK just bought smaller feelers. here are the #'s
Front
===== 1======== 2===== 3========4
===>0.0015=====0.003===0.004====>0.0015
====0.009======0.009===0.008=====0.008
Maybe I'm doing something wrong. I face point of the lobe facing directly away from the shim and slide feelers under. The less than means I don't have a feeler smaller than that. The bike runs. It fires right up. It wants to run high rpms if I rev it some and it hangs high till I kill it. Now I suspect that has to do with mixture screws and Idle screw being way off but I don't know for sure.

 

The idle is hanging because the carbs aren't sync'ed. You can't sync them with out of spec valve clearances.

It sounds like you're checking the valve clearances correctly; you'll need to do the "swap-n-re-read thing" for the ">.0015" valves.

YES THE MOTOR WILL RUN.

KEEP RUNNING IT WITH VALVES THAT TIGHT AND YOU WILL DAMAGE IT.

Quit trying to fix the carbs until you get the valves in spec; you won't be able to and you're risking burning valves right NOW.

Get the valves in spec before proceeding. Period. It's given you no choice at this point.

 

Damn that sucks. Well I guess I'll have to grab that tool to pull the shims. Unless you know another way.

 

Also if I pull out a shim can I pull all out and keep turning the motor without them in?

 

BOY I wish you guys would actually LOOK in "FAQ Suggestions." A lot of work goes into this stuff, believe it or not. Yes, there's "another way" although I'm not a big fan it does work: http://xjbikes.com/Forums/viewtopic/t=29209.html

And no, it's NOT a good idea to turn the motor over "shimless." Pull, read, replace.

 

I just reviewed my numbers with the manual. the ones with the .009 I really had to squeeze so I figure the whole exhaust run are pretty damn close to spec. Now the intake 1 & 4 are bad for sure. 2 & 3 are pretty damn good I bet 2 is probably closer to 0.004. I'm going to check these again later.

 

I haven't rode in 3 weeks.

 

.009 IS NOT "close to spec." NOT even. And close doesn't count, unless you really want to burn a valve.

And here's why: The TRUE specs are metric; so even .004" is actually OUT of spec ever so slightly at .1016mm, because it's NOT .11mm.

Specs are specs. If you expect to sync the carbs, GET THE VALVES IN SPEC. Not "close" IN SPEC.

There is only ONE size shim that will put any given valve within its specified clearance. Otherwise, you're not.

What I don't understand is why you would want to do this multiple times. Valve adjustment interval is 5000 miles, ONCE they're IN SPEC. Running them tight just means you'll be forced to do it again before another 5K. WHY???

 

Just pulled 1 & 4 they have 0 clearance and the shims are 280. According to the manual I should install 270 shims on these 2 is that correct? I will have to wait to do the other 6. I apologize for my impatience and ignorance. It's just killing me. this is my first bike. I hardly rode it so far and have spent more time fixing than riding and it's frustrating.

 

Autosdafe, please listen to agitated Wizard Fitz, he is trying to tell you something of critical importance to the happy life of your engine. Do it once, do it right and you will reap the benefits (as will your bike). DO NOT rush this, you will pay for it later. Build up some good karma for the good times ahead (assuming you follow the advice given). Best of luck and take it one step at a time by the numbers.

 

I am taking his advice and will proceed no further until all valves are in spec. Valves are all I'm going to work on for now.

 

Fitz isn't so much agitated as I am a bit frustrated trying to explain that some things are simply science and not a matter of "opinion."

Do it right, and do it once. Do it halfway, and you'll be back to do the other half PLUS.

I tend to get a little frustrated saying the same thing over and over; and it's not like I made it up or anything. Valves GOTTA be in spec or carbs won't sync; period. Valves gotta be in spec or BE IN DANGER of getting burnt the closer they get to dead tight. "VALVE CLEARANCES IN SPEC" is Step #1 in the "carb adjustment" section of the service manual.

Science, not opinion. Fact, not just Fitz. Wishing doesn't keep you from burning a valve.

 

I'm sorry Fitz I'm listening I'm just on a budget so tight I can't breathe. So I'm trying to keep the costs as low as I can. These valves will all be in spec before I go any further. even the 0.004. I will do this correct and not take a short cut.

 

Oh, and by the way: It took me nearly eight months to get my '81 roadworthy, even though the PO RODE it to my house. It was not safe, nor reliable at that point.

It is now. Don't rush; it's not worth it.

(The black bike --my '83-- took even longer. It was worth it.)

 

Wow God I hope it doesn't take that long for me. I'll post all specs and shims as soon as I get them off so we can see what shims I need for factory spec not close.

 

The most common mistake when measuring Valve Clearances is measuring the clearance with the Cam Lobe at 12 O'Clock, NOT actually Opposite the Shim.

 

if u just put it back together DONT TEAR EVERYTHING APART!!!!!!!!!!!!! u might get lucky.... i just bought an xj650 rode it home, started cleaning it up, rerouted the incorrectly routed cables, fixed the intake boots etc put it back together and had this exact same problem........ tore it back apart, cleaned the carbs put them all back together, new pugs, fired it up same rev problem.... bactracked everything i had done and it turns out that even thpough the trottle cable was as loose as it could be the bends in rerouting the cable shortened the travel just enough that it was holding the throttle open... i felt super stupid but was glad i figured it out b4 paying a shop!

 

PM me if you want to borrow the tool and keep a bag of shims. I can toss them in the mail tomorrow and you'll have them maybe on Saturday. I remember well trying to make it on a budget back in the day. My shims are for my 650 turbo so check to see if they are correct for your bike. I bought my shims from Z1 enterprises, cheapest place on the net. If I lend you the tool, you HAVE to send it back or I'll send the goon squad after you out of sheer principle<LOL>.

Gosh, you're from OH and I'm offering to help? The Wolverine Gods are going to be annoyed with me.

jeff- born in Ann Arbor

 

Here is my shim readings what shall I do with these and which ones are exhaust and which are intake.
front of bike
1======2=====3======4
zero===.003in==.004===zero
======.076mm=.102mm===
280===270====275===280===shims
carb side
.009===.009===.009===.009
.229mm=.229mm.229mm=.229mm
265====260===265===265===shims

 

ok so if i am reading correct i need :
1=====2=====3=====4
265===255===260===265
270===255===275===270
please someone make sure I got these right

 

Exhaust is by the pipes, yes, front of engine; intakes are to the rear, by the carbs.

I'll check the numbers for you when I get a sec. (currently at work.)

 

this may seem funny but I redid my math. if I take all my intakes shims and move them the other side the exhaust will be spec. And if I take 2 of my exhaust and move to intake side I would only need to buy 2 shims.
2 275 shims that is. I think I lucked out here

 

Sounds suspiciously not.

Invest in a "primarily" metric feeler gauge; they cost all of like $7. KD Tools' 2274 is commonly available: http://www.google.com/products/catalog? ... D0Q8wIwAw#

Then swap the shims until you're happy, and re-check. If you're doing the "converting metric-to-american" thing AND trying to do the math rather than use the shim chart (which is in my how-to BTW) you may have mis-calculated somewhere. Based on your previous posts, swapping the shims around as you're saying is not going to work. Putting a 280 where you need a 270 won't do it.

 

1 exhaust has 280 and zero gap
needs a 265
intahe has 265 with .229 gap
needs 275
2 exhaust has 270 and .076 gap
needs 260
intake has 260 and .229 gap
needs 270
3 exhaust has 275 and.102 gap
needs 265
intake has 265 and .229 gap
needs 275
4 exhaust has 280 and zero gap
needs 265
intake has 265 and .229 gap
needs 275
Now this is what the manual chart says just like the one in your tutorial. So as it looks If I was to get 2 275 shims I would have all shims I need. I am probably wrong but it looks correct on paper.

 

Your math has to be off somewhere in regard to the intake valves. They're NOT loose by double the spec.

Valves don't get loose; they tighten. I'm highly suspicious of a ".229MM" measurement on valves that normally run .11~.15MM. You initially said a couple of the intake valves were so tight you couldn't get a gauge under them, now all of a sudden they all have twice the spec'd clearance?

You've got a decimal point out of place somewhere. I was serious about a metric feeler gauge.

 

I'll echo Fitz, Autos, made the job so much easier. Wish I had purchased one years ago. And it's cheap.

 

Also, using either the metric or english feeler gauges make sure you don't get two blades stuck together. It happens.

 

Fitz I was backwards on the intake being tight. It was the exhaust. I figured the exhaust was intake cause I thought NO WAY could the intake be loose like that and the exhaust so tight. Ok let me clarify what I used. Originally I had a sparkplug feeler. The bike was warm when I first read them and once it cooled down my .11 feeler wouldn't work.I went and purchased a feeler designed for this. I never knew they went so small. When I went through with the right feelers and read them right things looked all different. I know it looks wierd that the intake is soooo off. Thats why I kept thinking maybe I'm backwards on which is intake and which is exhaust. But if the intake is near the carb then these readings are exact. I'd swear to them. I honestly suspect a PO did this and messed them up. But even if my gap readings is off +/- 0.01mm they still fall right in on the chart for those shim swaps. I have rechecked the gap multible times now and they are always the same.

 

oh yeah it was 0.11 inch sprak plug feeler.

 

The motor would have been making a terrible racket with intake valves at TWICE their specified clearance.

If you're absolutely 100% sure you're using the feeler gauges correctly and you really DO have .22mm (almost .23mm) intake clearances, then proceed.

I'm still not convinced. Highly doubtful a PO ever touched the motor, hence them being so tight. Plus you were reading WAAYYY tight on the intakes, now you're saying they're TWICE as LOOSE as they should be. Something doesn't add up.

I would honestly get a metric feeler gauge and re-check. ESPECIALLY after adjusting but before you fire up the motor again.

 

Way too tight when you look at the motor backwards LOL Yeah I was foolish when I first looked at it. And it did seem to be a noisy engine but I thought it was me cause this is my first ever motorcycle. There was evidence on the bolts on the valve cover of being pulled off many times before I got the bike. I could see someone who never knew what they were doing messing up the shims. I'll buy a new feeler after I get the shims done to double check my readings. Yeah this looks crazy insane on these readings. I was shocked too. My first readings were all wrong just ignore them.

 

Oh yeah Fitz you may not remember but when I did my clutch I found all my clutch plates aligned to the hub DOT by the PO. Makes me think he didn't know how to do things right so he could have done the shims wrong too. I think I am the luckiest man ever here on this bike. Lucky to have found the shim issue and lucky I may have the shims already.

 

Yay I got a new probablem!!! Just tested my ignition coils and the secondary coils are dead to the world!!! Yay more stuff to buy, but now I know what caused some of my other issues.

 

Ok so I have shims on the way. Found local shop with plug boots for $2.60 a piece. Hope to be riding by the end of the week. Fingers crossed.