Runs great/Starting nightmare

OK.
Carbs clean.
New intake boots.
New starter brushes.
New starter relay.
Mixture 3 turns out.
Not synced yet.
Float bowls adjusted I think.

After it is started for a few minutes, it runs great and idles good.
Starting it is next to impossible.
Fires right off but it only runs a few seconds and is VERY sluggish or doggy.
If you can message the throttle and choke a minute or two, it smooths out and starts with the slightest touch to the starter.
But if it dies, your done.
Could the float level be too high? flooding..
Just a sync problem.
You'll hear one cylinder trying to fire and one warm pipe.
Then maybe 2 warm pipes.
It's not speratic. It's the same sylinder firing or not fireing.
What do you think?

 

Is this common?I went through this last year alot... I was thinking the carbs just need to be jetted / Synced...

 

I wish I knew.
After the carb cleaning and new boots, the bike runs 100% better.
Alot stronger than before.
If It would only start.
This morning I went out to start it, and it fire right over.
But hardly enough torque to stay running so it died.
I cranked and cranked, with a charger on the battery since I ran it down.
1 cylinder was fireing.
One warm pipe. Starting spray had no effect.
Got fed up and went fishing.
5 hours later, same thing as when I left, 1 cylinder fireing.
had a few new plugs.
Put in 2 and it started again.
shut it off and put in the third. fired it up this time.
Alittle sluggish but this time it ran for the 2 minutes that it takes to run great again.
Now you touch the starter and it's running.
Let it cool off again and your out of luck.
I still think it's flooding, maybe.
Help...!!!...

 

Another thing it did was the occational loud pop from the exhaust while cranking the nearly dead bike.
What would be the first thing to look at??

 

Reverse the COILS.
Unplug the two Coils from the Wiring Harness and SWAP the Plug-in's around.
Now see if you are getting the sporadic fire on a different cylinder.

When it won't fire COLD ... you MUST troubleshoot the Enrichment Circuit Fuel Supply.

Are the Metering Ports at the BOTTOM of the Fuel Bowl -- Open -- and allowing Fuel to rise within the very small WELL in the wall of the Fuel Bowl?

Is the SIPHON TUBE(s) clear ... and allowing Fuel to be drawn-up from the WELL to the TOP of the Carbs?

If you have a clogged SIPHON TUBE or LOWER BOWL METERING PORTS ...

The bike is never going to have an enriched start-up mix and be a miserable beach to get started.

 

I would definitely recommend setting the floats correctly and synching the carbs properly. Both of these can be done in the back yard with the same amount of skill it takes to clean a set of carbs, but if your bike has YICS you'll need to either buy or make a YICS tool (making one is a bit more difficult, but it'll save you some cash).

Getting these two things out of the way will narrow down a few things. Now, hopefully it's actually possible to sync it when it's such a pain to start.

Next, since you're going to have the carbs off to set the float levels anyway, double check that your enrichment channels are clean. I have a feeling something isn't quite right there and it's causing some of your cylinders to fire cold or even flood.

Good luck.

 

This is going to mean there is a mixture problem. I've had popping from rich cylinders and lean cylinders.

 

That's what I would say, often when people think they cleaned their carbs, they really didn't get them good enough. All those holes have to be blown out with compressed air or poked through with the small carb sticks cleaning tool you can buy. Not only the ones in the bowls, but all the little holes in the carb bodies.
It sounds like some of the carbs aren't getting gas through the choke circuit. Those little holes have to pull gas up to the top front of the carbs to fill the orafices of the choke circuit. When you pull open the choke and that slide moves back, it flows gas down in front of the butterfly's to give you that enrichment you need to start a cold motor.

Often folks don't get carbs cleaned enough and varnished over gas does a great blockage job on orafices. I like soaking carb bodies (not diaphram's or any rubber in Laquer Thinner) it breaks down gas nicely. Then blow them out good with compressed air.

 

I know the float bowl jets are clean, I soaked them in carb cleaner and could shoot cleaner through them.
And the tubes running into them were free also.
Atleast when I put them together.
As I said earlier, it seems to run great after it's warm.
It seemed to start great the first time I started it after reassembly.
Much better than now.
Yesterday was the first time I actually road it.
I'll check it out again when I remove them.
I was worried that the float were alittle high when I put it back together.
Is it possible that that could cause this?
I've been running it with an OLD mower gas tank and I did put some heavy seafoam through it using the old plastic tank.
Could I have loosened up gunk from the tank and messed up the carbs?
I am running a fuel filter.

 

Just make sure when you clean your carbs, and spray cleaner through, pull open the choke circuit so it get's some cleaner to, or else the slider will keep those passages from getting cleaned.

 

Here's a cheap test to see if the passages to the top-end are open and the Enrichment Circuit is being supplied with fuel.

Using some FRESH High-test gas. Get the bike fired-up and cruising nice.

As you are enjoying the cruise ... Open-up the enrichment ... depending on how well you tuned-up the bike ... there should be a noticeable change in how the engine's performing.

If nothing happens at all ... you probably have some un-clogging to do!

 

I can kill the engine by hitting the choke while it's sitting on the senter stand if I don't get the RPM's up.
As much time as I spent cleaning them, I can't imagin them being dirty.
They were spotless and I checked every passage multiple times as it went back together.
The first day I got it together, it fired up perfect.
After it ran a couple minutes, it took very little choke to kill the engine at idle.
One thing I did was to add a stronge dose of Seafoam to the plastic mower tank.
Ran it for a few minutes and it sat for a few days.
The next time I went to start it, I had a bear of a time starting it.
I added gas to dilute the seafoam and it gradually cleared up.
Hasn't started good since.
It smoked prettty bad with the sea foam before the straight gas got to the carbs.
The tank was well used.
Could I have regunked it?
Maybe I'm grasping at straws here but the way I did start it was to replace a couple of spark plugs old but unused spark plugs.
Maybe I just fouled my plugs.
The plugs in the bike were years old but with not alot of miles on them.(I did plan on replacing them.)

 

Entirely too many variables to even begin making any useful suggestion other than:

Re-tune with clean, fresh gas ... and GAS alone!
Set the Pilot Screws to between: 2.75 & 3.00 (Split the difference between)
New Plugs w/ right gap
How's it run like that?

We'll put it on the edge ... as soon as we find an edge to put it on!

 

I had a similar problem where the first start of the day I had to use quick start spray and after that it was usually fine as long as the engine was warm. I finally had some time and decided to look into the problem. One cylinder would stay cold while at idle and the rest would get hot so I decided to pull the plug and see how it looked. It was moist and black. I went to the local yamaha shop and they suggested to change the plug caps and go 1 higher heat range. I did this and have had little to no troubles getting the bike started. Hope this helps
jason

 

silly question - I got some new plugs - I'm assuming that the small screw top (opposite gap end..) needs to be removed exposing the small threads - or does this stay on? I haven't tried - but it seems the plug cap from the coil wire wouldn't fit over that larger top...

 

You state in the first post that you haven't yet synced the carbs. This to me would be a priority. If the choke kills it then it is running too rich but without syncing, then it may only be one or two pots running rich.

Another helpful tip would be review your starting procedure. I have two XS 1100's that require a totally different procedure for starting. One requires choke and a twist of the throttle. The other is entirely different. Any twist of the wrist while cold will result in a lot of cranking and no fire. Very similar to your symptoms. It tries to fire straight up but is usually just firing vapours in the ports and never fully catches. Once these vapours are gone opening the throttle reduces the vacuum pulling through the pilot circuit.

I start it just by pulling the choke and pressing the starter without touching the throttle. It goes through the vapours then a second later sucks a fresh burst of gas and fires up and runs perfectly.

Took me two weeks to break my habit of opening the throttle in the starting procedure and have never looked back.

But, definitely go the sync first. It's worth the effort.

 

Canaweb,

You are correct - some pliers and some elbow grease takes them right off.

Rob

 

Yes, they need to be removed. Be careful though. I had a set of NGK plugs that were sub branded as Nissan Genuine plugs. The caps were fixed on these and had no removable caps. Twisted the top clean of them. :cry:

 

The plug-ends come off and just the threaded posts remain for connecting the plug cap.

You don't need to save the barrels.

 

It depends on the caps. Before I changed mine two needed the tip and two didn't.

 

Well I've fired it up 3 times, cold since last night.
After starting it so long with dirty carbs and cracked boots, I was in the habbit of alot of choke on starting.
It seems that if I give it any choke on the first crank, it floods.
Now I just hit the starter and it fires right up.
I have to let it idle for about 5 to 10 seconds before lightly applying some choke and adding a little RPM.
It will idle with the choke on but you have to add alittle RPM while moving the choke up.
I'm sure alittle fine tuning will help.
I was just alittle impatient since I've spent alot of time on the bike this winter and am really ready to do some riding.

 

If that's what it's doing ...

The mechanical Idle setting needs to be set. You need look at the little shelf, on the linkage, that the very end of the Manual Idle Adjustment Rod touches when the rod is screwed-in to increase the idle.

Look to see the end of the rod engage the shelf and MOVE it. When the ROD is turned IN and the LINKAGE MOVES -- give the ROD -- 3/4 of a turn IN ... causing the Butterflys to just crack open.

Set the IDLE for 900 - 1050 ... THEN -- adjust the Mixtures for BLUE or best idle Tweaking.

I have a feeling you'll be On the EDGE -- very soon!

 

I most have done something right.
After new plugs and a carb synch, it starts in 70 degree weather with a touch of the starter and no choke.
You have to give it alittle choke to throttle it up but after a minute it's go time.
Now to get the paint on and tie up a few loose ends.
I'm running alittle long on this project but it keeps growing.
You know how it is, if you do this, then you might as well do that also, then that, and so on and so on......

 

i have just got my first bike, it is a 1981 xj 650 and was running great when i bought her but after replacing new carb rubbers i am having the same problems as a you had.
can you tell me what exactly you did to fix the problem.

please note that i have not got any experience in mechanics but changing the rubbers looked like a simple job, now it is a tramp to start but will run greta when warms up.

i see about adjusting carbs but don't know what screws to adjust the 2.75 - 3 turns out.

IS it best to let a bike shop to do it ??? i would rather learn myself.

this went from a great starting bike with cracked and holed rubbers to a nasty starting ,popping, stalling bike when the rubbers was replaced, all in one day.

can't get my head around what earlier post says.

Set the IDLE for 900 - 1050 ... THEN -- adjust the Mixtures for BLUE or best idle Tweaking

what is blue? :?

any help please, OR should i walk away as i am a dodo.....

only have the bike a month and needs tidying but would like to get this sorted quickly and do not know any technical stuff about bikes.
IT DID start better before i screwed it up.

 

Woodvale:

Your bike WAS "Tuned" to compensate for the "Cracked and holed rubbers".
It's likely (if not certainly) that the Bike needed to be RICH to handle the extraneous AIR getting-in.

Now, that extra AIR has been eliminated by the New Parts.
You have to make an adjustment to the PILOT System to correct for less air being introduced.

Look at the Carbs where they are attached to the Engine.
Look at the Chrome Top of the one on the Left Hand side. (Viewed as if you were seated upon the motorbike)
To the front of that Chrome Cover and slightly below is a metal rod which activates the "Chokes" (Enrichment Valves)
That Rod passes through a Pillar on each Carb.
At the base of the Pillar is an Adjustment Screw.
That Screw regulates the amount of AIR that rushes into the Intake and draws-up FUEL from the PILOT JET reservoir.

Making adjustments to that Screw determines how well your motorbike will Start and Perform.

IF the Slots on the Screws are visible:

Clean-out the cavity which each of those Screws are in.
Place a drop of very thin machine oil in atop the Screw.
Fabricate, by grinding, a screwdriver, which will fit the Slot on those BRASS Screw tops, with the utmost precision.

It is vitally important that the Screwdriver does not have ANY movement when the tip of the screwdriver engages the Screw slot; otherwise the soft Brass wings of the Screw will deform or bend before the BODY of the Screw is moved.

Do NOTHING if the Screws DO NOT MOVE and feel stuck or frozen.

Should they move for you:

Turn the Screws IN ~> Clockwise; Very, very gently until the Screw reaches the BOTTOM.
Observe the position of the Screw Slot.

Clean-out the cavity above the Screw Head.
Re-oil the cavity.

Turn the Screw OUT ~> Anti-Clockwise; 2-7/8th -to- 3.00 Turns OUT

Do each one and report your findings.

 

i will do that,
the bike is at a friends house at the minute as i am going on holidays for a week and my shed at home is not very secure, i will report back as soon as i get her done. probably in a weeks time.

thanks for the speedy reply

can't wait to get it running well.

 

btw, i was just talking to the guy i bought the bike off.

he said that he never had the carbs adjusted and was running fine when he stopped using the bike 5 years ago when he had his license took of him.
he reckons the carb rubbers were good then.

I still plan on having a go at adjusting them anyhow but am worried that i have done something wrong while changing the rubbers.
i would be fairly certain all the joints and clamps are making a good seal but i did not even remove the cables from the carbs and just moved them out of the way.

Is it possible i could have knocked the adjustment out while changing the rubbers?
As i said this bike started and ran great before i worked at it (typical)

any way i may be able to access the internet while i am away if you have any more comments for me.
Either way i will report back to give results of adjusting.

FAO RICK,,,,IF the adjuster screws do not move what am i to do then?

does it matter where you have the fuel valve when starting?

does it matter which cyl the hose from the fuel valve to the carb rubbers goes to? its on cyl 3 at moment.

will i damage the engine if i ride it like this before it is sorted properly?

One more question,,,

Is the engine and gearbox oil all the one as i see a window close to the rear brake pedal and an oil filler above it but would like to know if it is for engine or gear oil or BOTH.
what sort of oil to use also.

THANKS in advance for all your help so far, this forum is great.

i hope to get a workshop manual soon but would like to get some minor jobs done first.

 

If the bike sat for 5 Months ...

I'd recommend removing the Carbs and doing a 100% Thorough Cleaning!

5-Years???

I can't imagine that the bike would run ... unless the PO did a Spectacular JOB of "Laying-the-bike-up"

What is your situation in that regard?

 

It looks like the bike was just fired in to a shed.

in fairness it was dry but it was dusty and rust piitting.

The day i went to look at it the fuel tank was dry, he put some petrol in it, put jump leads to it and turned over for 5-10 seconds then fired right up.

ran great and had good power.

i then collected it a few days later and it fired up again straight away.
at home i went out every day or two and started it and rode it a short while (5 mins or so).
last week i fitted the rubbers and now you know the story on that.

is there much that can go wrong if i decide to clean the carbs or could a monkey do it.
I will get a look at it next week when i am back, am leaving later today.

 

I've been "Monkeying-Around" with Motorcycle Carbs for some time. It's not that the process is overly complicated. The issue is dealing with component parts which have have had the chance to become difficult to disassemble for one reason or another.

One reason is age.
After many years of NOT being moved; the parts are reluctant to be withdrawn. Mostly because oxidation has frozen them in place.

The other reason is damage.
Brass bits and imprecise fitting tools.

The screw heads on some bit that ARE stuck are likely to have been damaged if someone attempted to withdraw them with ill-fitting tools.
This makes the project one of REPAIRS before the Cleaning begins.

How well you are able to dismantle ONE or the SET is dependent on their condition and your skills.

Both Scales are "Sliding scales."

Well maintained and undamaged bits ... along with advanced skills render the job easier than doing the job with inexperience and facing one obstacle after another.

 

I remember a past posting of someone that wasn't getting the carbs to fully seat into the intake rubbers. You may have noted the carbs have a grove cut into the neck that seats into the rubbers, it has a mating ridge inside the rubber to lock the two together. It's a good push to get them together correctly on older rubbers, haven't had the pleasure to try new ones, but could be one area of problems.

I don't think anything could get knocked out of adjustment, you may have a float valve hang or a cable fall out of position.

If the carbs don't have any fuel in them you should be on "prim" for a bit. Normal daily driving leave it on "on". Our valves are vacuum operated and fuel should not flow in "on" or "res", but fuel will flow in the "prim" position anytime (motor running or not).

It's normal for it to be on # 3 cyl, but I guess you could put it on any of the others, but why change it???

I wouldn't push it. Mines has run on 3 cyl after reinstalling the carbs, but fixes itself once the fuel gets flowing properly.

Yes the crankcase, clutch, and transmission share the same oil. It's motor oil not gear oil. The gear oil only goes in the rear wheel drive assembly.

Based on Yamaha specs either SAE 20/40 SE motor oil or SAE 10/30 SE motor oil depending on your climate. If you're in a hot climate some are using up to 20/50 oil.

The sooner the better, you will have all the technical specs in front of you with reference drawings of how things go together. I would look at getting the XJCD great info with parts cross reference.

 

Just back home again after lifting the bike.

I looked at the carbs and think i see the screws that adjusts the carbs and they have been chewed at a bit before although they should still be OK.

Anyway, i started it before touching anything and without the choke on, It cranked right up and ran smoothly although i did have to add a little choke to keep her idling until warm up.

I am going to leave the adjustment for a few more days until i see if it was a one-off or if it is OK.

The other thing is that i took it for a drive and the power was great but after aboutr 1/2 a mile the whole bike died.
no electric power at all, i rang my mate and he came in the car but before he arrived 5 mintes later the dash lights came on again but when i went to crank it the oil level light came on so i added about 200 ml of oil and it cranked right up again.
We drivre it about for half an hour or so and tried to wiggle wires to find the reason for power loss but could find nothing.

If someone could please tell me what grade of oil to put into the engine as i see it takes 2500ml but do not know what grade.

Also is the 2500ml for engine and gearbox both as it looks like it is.

I know this is a silly question to those who know but it is my first bike.

 

Not at all silly!

The engine and gearbox are combined. They share the motor oil.

20W/50 This time of year works well. As the time rolls 'round to Fall you can try something less viscous.

 

Thanks guys for all the help.

I have just noticed that Nick had answered my last question but as i logged into the site it brought me to page 2 and did not realise there was a third page of posts.

Anyway i now reckon that the tank valve had been left on prim and that the carbs were flooded.
It has started fine since coming home and have left the valve at ON.

I am going to change the oil in the next day or so.

MANY THANKS again to you all.