First REAL ride - engine is racing

I took it out this evening for about a half an hour and got it up to highway speed for the first time. Seemed like it ran pretty well, although I really have nothing to compare it with, since this is my first bike.

As the ride progressed, however, the idle speed started to rise. As I sat at a light it would run at about 2000+ then settle back down closer to where I had it set while tuning it up - about 1100. By the time I got back home and sat in the driveway for a minute, it was closer to 2500 and not dropping. Seemed like it got a bit hot as well. Not surprising, I suppose

So, I've rebuilt and tuned the carbs and adjusted the valves. Not so sure about whether I have the idle mixtures optimized, but the idle been staying put while driving around town at 30 mph or less.

Maybe this is normal after a carb overhaul and I just need to go back and tweak again???

Thanks.

 

Normal.

If the Diaphragm Pistons aren't sticking, ...
And, ... there's no air leaks ...
The matter is Fine Tuning.

Sync, Idle Mixtures and a couple of Plug Chops and you should be good to do.

I guess yer gunna haffta fine a way tuh git uh Y-I-C-S Tool anne one of them-there color tuning sparkin' plugs, ... eh?

 

Good news or bad news first?
Good news every body has needed to clean ther carbs.
Bad news you need to clean carbs.
There are many many forum links with helpfull info. Search for idle curcut cleaning. It is the most important for proper Idleing. I will atempt to insert a link here for you of just one fresh talk about your same problem. I hope this works!
http://xjbikes.com/Forums/viewtopic/t=27368.html

 

Bay.........did you get the engine (carbs) vac-synched properly? An out-of-synch engine will display all kinds of symptoms that can mimic other "real" causes.......


RICH, LEAN, or possibly even ritually UNCLEAN or OBSCENE: THE CARB REBUILDING FAQ:

Question #1: Why Isn't It Running Right?:

Below is a semi-useful "general rules-of-thumb" list to help you recognize and diagnose fuel-mixture problems.

All of these descriptions assume that the carburetors are cleaned and operating properly, are stock (no jet kit), the valves are adjusted properly, and the engine has been synched.

If any of the above procedures, tasks, actions, or activities have NOT been checked or performed, then do them first, or otherwise all your other efforts will barely even give you "casino odds" at striking it rich and determining what the real cause(s) of your symptoms are......


Typical Symptoms of a Lean Fuel-Mixture Condition:

- Poor acceleration; the engine feels flat.

- The engine won't respond when the throttle is snapped open, but it picks up speed as the throttle is closed. (A too-large main jet also mimics this symptom.)

- Idle speed falls after you blip the throttle, then creeps back up.

- The engine runs hot, knocks, pings and overheats.

- A lean pilot circuit condition can be responsible for a creeping or hanging high idle, where the rpms stay high then slowly drop down to the set point.

- The engine surges or hunts when cruising at part-throttle.

- Popping or spitting through the carb occurs when the throttle is opened. Or popping and spitting occurs through the pipe on deceleration with a closed throttle.

- The engine runs better in warm weather, worse in cool.

- Performance gets worse when the air filter is removed.



Typical Symptoms of a Rich Fuel-Mixture Condition:

- Engine acceleration is flat and uneven and loses that "crisp" feel.

- The engine "eight-strokes" as it loads up and skips combustion cycles.

- The engine's idle is rough or lumpy, and the engine won't return to idle without "blipping" the throttle.

- An overly rich pilot mixture is usually the culprit when the idle drops low then slowly recovers.

- The throttle needs to be open continuously to maintain acceleration.

- Black, sooty plugs, a sooty exhaust pipe and black smoke from the tailpipe that stinks of unburned fuel.

- Poor fuel economy.

- The engine works better when cold. Performance falls off as it warms up or the ambient temperature rises.

- Engine performance improves when the air cleaner is removed.



Some common causes of a high idle:

- A lean air-fuel mixture condition, which can be caused by a variety of problems......vacuum leaks, plugged or too-small fuel jets, etc. Old or "stale" gas may also cause a lean fuel-air mixture to occur temporarily (until the fuel is used up!).

- A vacuum leak somewhere in the intake system.....intake boots, internal o-ring seals, etc.

- Mixture screws not properly set or adjusted.

- Vacuum piston sticking or stuck in a partially raised position.

- Idle speed screw set too high, or set to create a "proper" idle speed when the engine was cold (and thus results in a "high idle" once the engine reaches operating temps). The idle speed when the engine is cold should be modulated via the use of the choke (enrichment) control system.

- Butterfly valves opened too far; synch screws out of adjustment.

- Throttle cable wear, adjustment, or throttle lever brackets installed incorrectly or interfering with other nearby objects (cylinder head fins, etc.).

- Choke (enrichment) circuit is stock "open"....this can occur even if the choke lever is rotated to the fully closed position, if for some reasons the choke plungers are not fully closing (cable wear, cable adjustment, bent finger brackets, or installation problems).

 

I agree; sounds like a simple sync issue to me or one carb is way off, mixture wise OR you have a high float. All it takes is one carb to "drag" the others UP.

I know we'ver probably discussed this already, but how did you do your float levels?

 

I don't think you read my post, brother. I just did a complete rebuild on the carbs. They're as clean as an operating room. I appreciate your reply, though...

...as I do all others. You've helped me along the way but I know there's no way you can possibly remember the details of my project. Therefore I will post the important details and I'll try to answer any remaining questions.

Carb rebuild
- thorough cleaning with dip and spray; cleared every passageway using appropriate size wire or drill bit (without enlarging), then sprayed again
- carb kits
- new manifolds and screws installed with black RTV on both sides of gaskets
- polished vac pistons
- replaced throttle shaft seals
- replaced #1 carb with a #4 carb from another set; plugged and sealed outside fuel port
- adjusted floats (leveled) on the bench using a test tank and sight tube; struggled with this but eventually had everything right on the money

Carb adjustment
Vac Sync
- built my own YICS tool from internet plans
- built my own 4 tube vac gauge from internet plans
- first attempt at syncing
- abandoned homemade YICS tool in favor of MMO-soaked cloth strips stuffed into YICS gallery
- second attempt at syncing
- abandoned homemade vac gauge for a single dial-type vac gauge and synced (at 1100 rpm) using Rick's tutorial for this method
- third attempt; I believe the bike was darned pretty close when I finished

Pilot Mixtures
- initially adjusted these by feel because the bike wouldn't idle without the choke on
- later attempted to use a ColorTune plug but had quite a bit of trouble with this
- mixtures have not been touched since bike was synced

Like I said initially, I'm not real confident about where the pilot mixtures are set. However, things couldn't have been too far out of whack considering how nicely it was running and idling while driving around town, right? So I'm wondering what changed during this ride. Is it possible that the sync screws/springs/etc are just "settling back in" after the rack was broken apart and reassembled?

Choke has also been working. I've been starting the bike with full choke, then pulling it back to about 3/4 almost right away, then off within probably a minute of idling.

So that's a recap. I hope I answered all questions. Thanks.

 

riding around town for short periods or idling in your driveway doesn't get it hot enough to finalize your fine tuning. Take it out, run it good and hard until it shows the high idle, bring it home and then go about synching, and mix adjusting.

It's dime width turns to the mix screws and maybe 1/2 turn on the idle speed control screw.

As I've seen posted somehwere here before.... You're in the ballpark, now let's find your seat.

 

GOOD recap.

From what I can tell you're nearly there. The bike will be MUCH MORE sensitive to mixture and sync once it's fully warmed up; so unless something has come loose or sprung a leak I think it's just a matter of fine tuning.

I would do this: Check the position of the mixture screws, and set them all to a "happy average" based on where they are now.

RE-vacuum sync, and then install a new set of plugs, and get the bike good and warmed up, and see where you're at.

 

Great! Thanks, Fitz and gamerover. I'll report back.

 

I'm working on retuning right now. The mixture screws were all very close to one another at about 4/3/4 turns out with the #2 screw at 5. I changed that one to match the others.

I'm about to sync now and decided to do it with the tank on the bike but propped up in the back so I can reach everything. I always used a test tank before because I didn't have a working fuel tank for the bike. (See other mournful threads.)

As I was starting up the bike with the vacuum gauge on the #3 port I was having trouble getting it to run evenly. It just occurred to me that this is because there's no vacuum controlling the petcock anymore. Can I just switch it over to PRIME or do I need to hook my test tank back up?

Thanks!

 

Prime is perfect for this.

 

I THINK I understand how to do this, but I just can't seem to pull it off for some reason. I'm using a single vacuum gauge.

Check vac on #3. Idle at 1100rpm.
Check #2. They match.
Match #3 to #2. When I do this, the idle speed comes up but the big speed screw is all the way out so I can't slow it down.

Now what do I do?

 

Gotta match #1 and #2 FIRST. THEN match #2 to #3, number two will bring number one along.

Matching #4 to #3 is a separate but important function as well.

Then go back and check 'em all again, remove the YICS tool, and adjust the main idle knob accordingly.

 

sounds like what happen on my bike, at first it just idled great 1,100 rpm and then when i was at a stop light after about a half hour of driving, both cruise and fast, just sitting their, the bikes rpms start climbing, only then did i realize my choke was on halfway......

 

That could happen easily but isn't what's going on in my case. I've been minding the choke pretty closely.m Thanks.

 

I've seen it described the other way a number of times, but what you're saying makes more sense. There really isn't any point in checking #3 until you're ready to line 1 & 2 up with it, is there?

I actually decided to adjust the screw between 2 & 3 because I figured something was out of whack there. Then I was able to get everything pretty close. It's certainly not an exact science. Somebody should design a computer that controls ignition on vehicles...

I just got back from a test ride and it seems to be running a little better. I have what I would describe as little bit of "spitting" or "sputtering" when the rpms approach 4000 or so. I still have power and can accelerate at that point but it isn't quite as smooth in that range as I think would be ideal.

When I really open up the throttle and I hear the engine roar, what's happening? Is something opening up and delivering more fuel in the carbs?

Regarding idle speed: The idle did come up a bit as the bike warmed up but it only climbed to about 1500 as opposed to 2500. However, it's a cool night so I'm not sure how it will be when the air temp is higher. Should I adjust the idle speed downward to 1100 when the cycle is warmed up? I'm sure I can compensate with the choke when it's cold.

Tomorrow will be my first longer ride. I'm heading down for a funeral in my hometown about 4 hours south of here and returning on Saturday. The weather will be nice but cool - upper 50s. Any recommendations for a trip like that, what I should bring, etc?

Thanks!

 

Sounds like you're closing in on it.

#3 HAS NO adjuster of its own, its only adjustment is the main knob. If you're using a single gauge, you only need to check #3 as your baseline.

The screw between 2 and 3 is #2's adjuster; like I said you sync one to two then that screw will bring them both along to match 3. Then you match 4 to 3.

Yes. You're getting up on the mains, and as the engine begins to make some serious power, the vacuum-operated CV carbs finally decide to pick their slides up for real as you hit the "sweet spot" in the powerband, from 6K to 8K. Torque starts to level off at 8K but the actual HP keeps right on increasing to peak AT the 10K redline. These motors love to rev. And even with the stock exhaust they make a nice howl above 6K.

Adjust your idle speed once the bike is fully warmed up.

Take your rainsuit. Then you won't need it; leave it home and you'll get wet. Now that it's suddenly gotten colder, be sure to double-check your tire pressures before leaving. The onset of the cold will cause them to get soft. Might not hurt to lube the chain too.

 

Thanks, Fitz. I'll try to clean up my nomenclature on the sync screws. I actually do know what they control but I didn't describe that properly.

On the topic of tire pressure, the dealer mounted these new tires for me and they filled them to about 32psi. The tires (Dunlop) say a max of 41. How much pressure do you keep in yours?

 

I generally run 26-28 in the front and 30-32 in the rear; and I'll take the rear up to 36 or so if I'm running "touring loaded" or 38 for carrying a passenger (plus turn up the rear spring preload.)

32psi in the front is way too hard.

 

Since this article was first published, ... Members have added their insight to make the process much easier.

The Member who Suggested using an Aquarium Air Valves Gang was a HUGE refinement.

So, this is going to get to get you, .... Synchronized.

http://xjbikes.com/Forums/viewtopic/t=2 ... ethod.html

 

Yes, this was the document that I read before deciding to try the one gauge method. Thanks. A question, though: when you say...

...do you mean using the throttle or the idle speed screw?

 

Make and use a Vacuum Restriction Device.

It settles-down the Fluctuations to a readable scale.
If the gauge is on the Pin and Spring ... you dont know.

Epoxy some Carb Red Tubes in the center of some Hose Unions and clip them off to make the Diameter of the Hose much smaller.

Reducers/Restrictors:

 

I actually had some vacuum restrictors on hand. They are basically the same thing as you describe except that the insert is brass rather than plastic. I also added a small fuel filter inline.

Are you saying that your instruction to rev it up was just to make it more readable, and that it's not necessary with the baffling?

Am I correct, though, that you should only use the idle speed screw to adjust idle speed during syncing and not touch the throttle?

 

You sometimes have to ADD Turns to the IDLE Rod to KEEP the Bike running.
Then, as the Pilot Mixtures are adjusted the RPM's rise.

Reduce the RPM's by Adjusting the IDLE ROD.
The Mission is to TUNE the Bike to be able to IDLE with the Throttles closed.
(Or with the most (my-nute) amount of AIR allowed to enter from Throttle Butterfly's Bench Synced with the the thin 3X5 Card.

The IDLE should be so good ... that the Bike can be left unattended and IDLE at 1,000 ~ 1150 without being touched.

 

I've been trying to figure out why my idle comes up when the bike is good and warm, but I think I just need to back the idle screw off at that point and see what happens. If I need to run with the choke on for a few more minutes after starting her up, what's the difference?

Once I get my tach fixed or replaced I'm going to give that a try. Thanks.

 

After second cleaning of the carbs, mine's racing as well. I have to theories for this:

1 - pistons sticking (even though they pass the clunk test)
2 - butterfly valves not closing properly (even though theyre bench synched and throttle adjustment screw is backed off)

I can say I'm 99% sure there are no air leaks on the manifold side of the carbs, and the butterfly linkages (where the v-rings are fitted) are sealed tight with RTV. Now, this may be a cause for the "sticking" of the butterfly valves, but I've checked that it does seal fully once the throttle is closed.

 

It's usually a sync issue; or if you had the butterflies off their shafts, it takes some real fine tweaking and fiddling sometimes to get them to fully close.

Shine a bright light from behind and look through the carb bores to check and see if the butterflies can each close fully. Carbs not perfectly aligned on the rack can cause the same issue, one binding and not closing, and it only takes one to pull the idle up.

 

I know what you mean. I did see a small shrivel of light when I held it to a light source, but then I just went to good old basics and tried to suck air through - guess what, no air until I open the butterfly valves or release the choke.

 

But even if there was some slight leakage around the butterflies that wouldn't explain why the idle speed rises when the bike is warm, would it? It would idle high all the time, right?

 

No. When the motor is cold, it wants an overly-rich mixture. It also doesn't respond to the mixture the way it does when fully warm, which is why you need the "choke" (enrichening circuit) when it's cold.