Yamaha XS 896 "Silver Bullet"

[2_DONE_THE_TON]

Dear Forum!

Its been years since I posted on here. Its amazing to login again and see that the community is still alive and well and keeps on making cool projects.
I have been busy with all kinds of things but was constantly chipping away on my Yamaha XS 896 project.
The project took so long since its been my learning project for my sheet metal skills and has been a steep learning curve.

I have been constantly learning and taking courses at Wray Schelin´s Pro Shaper workshop in Worcester near Boston.
The body of the motorcycle will be completely made from polished aluminium sheet metal.

Engine specs:
Big bore kit (896ccm,bored out XS850 cylinders)
Keihin CVK carburettors from a Triumph Sprint 900 (Main:120,Idle:38,Needle:N3RF) with K+N pod filters
3-1 Jama exhaust

Now I have been able to start the bike but ran into problems.
The bike only starts with starter fluid and kickstarter and electrical start combined.
The bike runs and idles on the carburetors.
I am using a small lithium battery, which seems to be drained very fast and cant turn the engine over strong enough.
I also tried to use the battery of my FZR1000 which has a bit more oomph but it is also unable to turn the engine over.

What would you guys recommend doing now?
Just borrowed a larger lithium battery and will try with that one, but I have the fear that I will need a way larger battery (which will be problematic fitting under the tank).

Thanks guys!

Carl

 

[adventurco]

Is it turning over slowly? If so the starter may be gummed up causing hard starting.

Ideally if your carbs are set up properly you shouldn't have to turn it over with the starter more than one or two revolutions for the bike to start up.

I would start by comparing the CCA/Ah of your batteries.

Keep in mind many folks ditch the electric starter for kickstart only for customs simply to get rid of the big old battery.

 

[2_DONE_THE_TON]

Hey Adventurco!

Thank you for chiming in!

Yes the starter could be an issue.
Before starting the bike myself I brought it to a mechanic here in Vienna that is specialized in motorcycle electrics.
The bike was impossible to start.

He found that there was very little compression on 2 cylinders which he traced back to two misadjusted valves (too wide open). He adjusted these valves via shims and the bike started up. Small lihtium battery combined with a 20Ah battery charger.

He also checked the starter and told me that there was a resistance problem and cleaned it out. He said that it will be hard to find any starters that don't have this resistance problem.
He also cleaned the starter and put it back.
I think I will order another starter and try if it will better my problem. It definitely spins over more slowly than it used to when I had the standard displacement of 750ccs.

Here is a small video of the bike starting up with kickstarter and electric start:

 

[2_DONE_THE_TON]

Hey Forum!

So I tested the bike with a new lithium battery I borrowed from a friend that has more oomph. The engine seems to be spinning more freely and I am sure that this is enough to start the bike.
I tried to cold start with no starting fluid but no success.
As soon as I used start fluid, spraying it on the KN filters the bike started easily.

I also adjusted the ignition so that it would align with the "1F" mark so it is spot on.Tried again with no starter fluid and just choke....just spinning no start up.
As soon as I added the starter fluid it started up easily.

Could this be a carb issue, maybe idle jets that are too small or too large?
As its only starting with starting fluid I was thinking that it doesnt get enough gasoline at idle....

Thank you for your help!
View attachment 241376

 

[jpmobius]

First, I suggest avoiding using any sort of starting fluid other than the fuel the engine is designed to run on. I realize that opinions vary intensely on this, but having designed and built engines for over 50 years, I've never used it. Any engine not starting pretty much straight away always had a dedicated problem somewhere, and when found, did start. I've also personally witnessed an otherwise perfectly fine Chevrolet marine v8 get completely destroyed attempting to start it on ether because the carb was gummed up from sitting. (bent a connecting rod). So, you've been warned, and that's the end of my rant!
In your video, the engine seems to run and idle good enough to leave the carbs alone for now except to check the chokes or enrichers. I'd want to isolate the ignition from the rest of the bike and test it. Just disconnect the ignition circuit from the rest of the electrical system, and run it on a known good and fully charged car battery (for example). That way, you can fool around starting it knowing with certainty the ignition is working and not compromised with your activities. Many systems starve the ignition when the starter motor runs, and high compression and/or increased displacement can severely increase this problem to the point of losing spark. Isolating the ignition will eliminate this if it is a problem. Old ignition systems can be very weak and produce pitiful sparks if not fully powered, and what may look acceptable with the plugs out can be too weak when installed with compression, a straining starter motor, and no help from the not spinning fast enough alternator. New systems can fail to produce any spark at all simply because the voltage is below threshold from the greedy starter.
You seem to have a somewhat slow return to idle (sketchy judgement from very brief video) so check for vacuum leaks. Shouldn't much impact starting unless quit a bit more severe than it seems in the video.

 

[2_DONE_THE_TON]

First, I suggest avoiding using any sort of starting fluid other than the fuel the engine is designed to run on. I realize that opinions vary intensely on this, but having designed and built engines for over 50 years, I've never used it. Any engine not starting pretty much straight away always had a dedicated problem somewhere, and when found, did start. I've also personally witnessed an otherwise perfectly fine Chevrolet marine v8 get completely destroyed attempting to start it on ether because the carb was gummed up from sitting. (bent a connecting rod). So, you've been warned, and that's the end of my rant!
In your video, the engine seems to run and idle good enough to leave the carbs alone for now except to check the chokes or enrichers. I'd want to isolate the ignition from the rest of the bike and test it. Just disconnect the ignition circuit from the rest of the electrical system, and run it on a known good and fully charged car battery (for example). That way, you can fool around starting it knowing with certainty the ignition is working and not compromised with your activities. Many systems starve the ignition when the starter motor runs, and high compression and/or increased displacement can severely increase this problem to the point of losing spark. Isolating the ignition will eliminate this if it is a problem. Old ignition systems can be very weak and produce pitiful sparks if not fully powered, and what may look acceptable with the plugs out can be too weak when installed with compression, a straining starter motor, and no help from the not spinning fast enough alternator. New systems can fail to produce any spark at all simply because the voltage is below threshold from the greedy starter.
You seem to have a somewhat slow return to idle (sketchy judgement from very brief video) so check for vacuum leaks. Shouldn't much impact starting unless quit a bit more severe than it seems in the video.

Dear Mobius!

Thank you for chiming in!
Also thank you for the advice with the starting fluid, I will follow your advice.

I already checked the ignition with a flasher to see if its ligning up with the "1F" mark which it now perfectly does.
I did this by removing all spark plugs and using the flasher gun on the ignition side.
The bike has spark on all 3 cylinders (Stock Yamaha XS850 TCI ignition is installed).

What I have measured is that there seems to be no charging happening. When the bike is running the voltage of the battery does not into the 14v area.
So my guess is that there must be something wrong with the cables coming from the generator up to the battery. A drained battery would of course cause no spark, so I need to look into this.

The slow return from idle is definitely there and I will investigate into vacuum leaks.Would you use brake cleaner to find the vacuum leaks around the carburettor?
How would you go about looking for choke/einricher problems?

I also thought that maybe my 38 idle jets are too small for the more free flowing setup I have so maybe exchanging them for 42s or 45s would help?

Thank you!

 

[adventurco]

There should be a section in your manual to test the stator output. Your charging issue will either be the stator output or the Regulator/Rectifier. Definitely get that resolved first.

As for vacuum leaks, spray any kind of solvent around the boots, any areas of the carburetors with a rubber part sealing it from outside. If the idle changes either high or low you that is a sure sign of vacuum leak.

I'm not sure where you got your jetting baseline, but I would certainly try upping the jet sizes if there is still a high idle after you have ruled out or fixed any vacuum leaks.

 

[jpmobius]

Trouble shooting and diagnosis is by far the most difficult task most bike owners have to deal with. You can be very skilled taking things apart and fixing them, but determining what actually needs fixing can be exasperating. So it's helpful to have a methodical approach. Engines are complicated in that they have several systems that interact with each other, often in ways that can be fairly confounding. I like to focus on one thing at a time, and use the process of elimination to focus in on the problem if my first 'theory' proves wrong. You can waste incredible amounts of time jumping from one guess to another.
So. . .
You have a starting problem. Why? Doesn't spin fast enough? Doesn't spark enough? Doesn't fuel enough?
You have a carburetor issue? Wrong jetting? Air leaking in? Starting circuit not working?
You have a charging issue? Alternator? Regulator? Wiring?
Whew! I'm tired just thinking about what what to do!
But it's not really that bad. Determine what to solve first, get that fixed and move on to the next. But what order?
Well, the charging issue is important, but it has nothing to do with the engine starting or running, so don't worry about it until you solve your other problems. Eliminate it for now by replacing it with known good battery kept fully charged. I like a car battery, fully charged, connected to a charger. Connect it to the battery on your bike. This problem is SOLVED now. Your bike now thinks its charging system is perfect, and it has plenty of energy. You can now troubleshoot the starter and ignition systems (or anything else) because you have eliminated your battery and alternator/regulator/associated wiring as problems.
So. . . carburetor. You KNOW the bike runs and idles more or less ok. So, starting the engine is NOT a jetting problem. Don't add another variable before solving everything else. If all you've done is increased displacement, likely (not necessarily) you'll keep the stock pilots. If it's cold starting only, focus only on the cold starting circuits. This will either be a choke or enricher circuit. A choke will have a manually operated butterfly across the bore. When engaged, the edge of the plate will be very close to a small hole in the side of the bore. This is the source of the extra fuel needed to start the cold engine. High speed air squeezing past the choke plate sucks fuel from this hole to start the engine, so make sure this passageway is clear. Enrichers use some sort of plunger valve to open a direct fuel source and don't need the extra butterfly. Either way, bypass the starting circuit by starting the cold engine with the air cleaners off, and momentarily putting your hand over the carb inlets while cranking the engine. This will cause engine vacuum to suck some extra fuel into the bore. If it starts or tries to start, you know where to look.
If that produces no news, go back to the ignition as noted in my previous post. And remember, a working timing light does not mean that plugs are necessarily firing. KNOW they are by actually seeing them spark outside the cylinder, and by isolating the whole ignition system when they are installed.
As for a potential vacuum leak, I like to use a propane torch (unlit!). when the engine sucks in the propane, it'll speed up like spraying flammable anything, but less messy. WD40 works well also. Makes a mess, but doesn't harm anything.

 

[2_DONE_THE_TON]

Thank you guys for your input!I will put all that to practice and dig into the carbs as mobius said.
Here is some eye candy for you guys.
This project has been my learning project for now almost 7 years. All the bodywork is hand beaten from aluminium (fairing 1.5mm, tank 2.00mm thickness).

 

[jpmobius]

Wow that's a lot of work! Nicely done. Definitely have to get it running properly. I failed to mention previously, starting fluid is pretty good for finding vacuum leaks if you still have some. It's ok as long as the engine is already running. When hunting vacuum leaks, be aware that air commonly leaks in at the throttle plate (butterfly) shafts/axles (and choke plate axles) if your carbs have them. This is rarely a problem except on very old (like old British cars) carbs, but I mention it because if you spray ether there inadvertently, you can be misled as to the location of an actual leak because some air always leaks at these locations. It's just too small to matter, unless the carbs get so used that the axle bores get wallowed out, or damaged from improper disassembly.

 

[2_DONE_THE_TON]

So I took some time and tested Mobius suggestion with using my palms covering after removing the Pod filters.
The suction was so strong when I tried it and my hands were full of gasoline,maybe I put my hands too long over them.
The bike made light starting noises but didn't fully start (just a start moment where it seemed to be starting).

Next I took out the plugs because I saw that my cylnder head was seeping oil from the seals surface.
I didn't bolt the cylinder head cover down because I wanted to see if oil was coming up there,now I now....
I am also sure that this fact fouled my plugs,making starting harder.

Next I started digging into my carbs,with focus on the choke and Idle jet circuits.
I will look at all the orifices and see if anything is plugged.


I removed the bar that connects the enrichener brass plungers.
Would you guys remove the choke plunger assembly?
My guess is that the assembly is screwed into the carb body.Has anyone of you removed these?

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[Luugo86]

Just tightening the cylinder head properly could completely solve your issue, great work on the aluminum

 

[jpmobius]

The plungers unscrew via the hex on the plunger body. Very likely they are a self contained unit with a piston that seals at the bottom against the carb body. There will be a passageway into the fuel bowl, and another into the bore. Both must be clear for the enricher to work (obviously). I am not super familiar with these specific carbs, so hopefully someone with more direct experience will chime in. As a general rule, however, I'd recommend rebuilding the carbs to eliminate them as a potential problem. And by 'rebuild', I really mean clean. Probably, getting the individual carbs separated from the assembly will be more work than the carbs themselves, as you only need to focus on cleaning and not complete disassembly. Ultrasonic cleaners are all the rage these days, but absolutely not necessary. Spray can carb cleaner (the kind with a straw) will work fine. Do NOT buy rebuild kits unless you need gaskets, and then you're better off getting factory parts from the manufacturer. Never replace any brass parts or jets/needles with anything but OEM. These parts do NOT wear out or degrade (ok, maybe in a million miles) and new after market parts are far inferior to clean old parts. Don't try to remove the throttles (butterflies) . Just remove the jets and emulsion tubes, and check you can get a clean stream of cleaner through all air and fuel passages. This takes patience and a dedication to being thorough. You need EXACT tools. Grind flat blade screwdrivers for a precision fit in the jets. You only have one try. Damaging a jet getting it out can be a real disaster. Also, grind any sockets you need flat on the end so the hex engages 100% on the fastener. Use 6 point sockets only. Sockets have a slight taper, which needs to be removed to get complete engagement on thin, delicate carb parts like those enrichers. Don't replace the needle and seat assemblies either. Take a small piece of steel wool and spin it on the seat surface with a flat tooth pick. Better than a new one. Take your time and be meticulous so when you're starting the engine, you KNOW there isn't a carb issue. I always go through the carbs on a new build whether I think they need it or not for this reason.

 

[2_DONE_THE_TON]

Dear Forum!

Thank you again for the answers, I will keep all that in mind when cleaning the carbs.I will focus on getting a clear stream of carb cleaner trough all orifices.
I took all the jets,slides,mixture screws out of the carburetor,being as careful as possible not to screw any of the heads of the brass jets up.

The mixture screw has 1 small opening going into the carb throat (with the peak of the screw slightly pointing out).
The idle jet has 4 little holes also opening into the carb throat.
I took all the hardware out and blew these holes clean with compressed air and carb cleaner.

Next up is the choke circuit.

 

[adventurco]

Not sure if this was mentioned already but since you are working with CV carbs, check the rubber diaphragms for cracks or splits. I always hold them up against a bright light and gently stretch the material outwards and look for light passing through.


Sent from my iPhone using DO THE TON

 

[jpmobius]

Not sure if this was mentioned already but since you are working with CV carbs, check the rubber diaphragms for cracks or splits. I always hold them up against a bright light and gently stretch the material outwards and look for light passing through.


Sent from my iPhone using DO THE TON

Definitely! All manner of intermittent and 'can't figure this out' issues from this. An obvious tear makes it not work at all, but a tiny hole can be not noticed and result in unfathomable behavior until you find it!

 

[2_DONE_THE_TON]

Not sure if this was mentioned already but since you are working with CV carbs, check the rubber diaphragms for cracks or splits. I always hold them up against a bright light and gently stretch the material outwards and look for light passing through.


Sent from my iPhone using DO THE TON

Thank you adventurco!I will check the diaphramgs for tears!

I already came pretty far with cleaning the carburetors.I took out all the jets,slides, needles and seals. I blew trough all orifices and passageways with air and carb cleaner. I also used a ultrasonic cleaner and the repeated the process looking for a clean stream of carb cleaning coming out of every orifice.
From what I see there was no plugged idle jet orifice or jet.

I decided for now not to split the carbs. There are some orings on the plastic connectors (fuel flow connectors between carbs also air vents) which probably need attention in the future, but for now I thought it would be good to focus on the idle + starting circuits. I also saw that I missed an Oring on one of the mixture screws, which I will order and put in the missing spot as soon as I receive it.

I however have problems identifying if the fixed starter jet is clear.
It is somehow hard to blow air or carb cleaner into the tiny fixed brass jet that is pressed into the carb body.
The passageway runs very complicated trough the carb body running by the brass choke plunger and then trough an orifice to the engine side of the carburettor.
I will try today again to blow trough the orifice on the engine side and maybe carefully run a guitar E string trough the fixed jet.

Cheers and Thank you guys!

 

[2_DONE_THE_TON]

Dear Forum!

Here a little update on my XS project.

I took a good amount of time to tear into the Keihin CVK carbs looking for any blocked orifices or jets or tears in the diaphragms.
There were no visible blocks or tears and I could see a clear stream of carb cleaner trough all the passageways.

Then I tried to start the bike and I was able to start the bike with no starter fluid but again only with combination of kickstart and electric start.
With electrical start, the engine would turn over a few times then stop and not turn over (just hearing the click of the relays). The kickstarter alone is super super hard to kick down (which I guess is due to the higher compression rate of the engine).

Also the enrichener seems now to be working fine and I am able to start the bike within 2-3 kicks (together with the electrical start). The engine clearly revs higher when I pull the enrichener and if I release it when the engine is warm the bike idles nicely.

I am looking to buy a "fresher" starter which I was able to source from Germany,which I will hope to help with the "weak" electrical starter.
My mechanic also advised me to shorten the starter cable ( I routed them very complicated so it is invisible) and use a thicker gauge which could also help the electrical start.

Then I started investigating into the charging system.
The mulitmeter would read 13V with an idling engine but also when I revved the engine it would start with 13.Volts.So no charging.
The regulator unit was also tested via multimeter and showed no problems.
I measured continuity between the 3 prongs of the generator and I had continuity....
So I pulled the generator and it is clearly cooked with clear marks and burned smell.
Fortunately I have a bunch of parts and could source a full unit from my basement which I will install in the next days.

View attachment 241525View attachment 241526View attachment 241527View attachment 241528

 

[2_DONE_THE_TON]

Hey forum!

So I had break trough with all the issues stated here.

I explained that my generator was clearly cooked and that I had a replacement unit in the basement.

I took the unit,cleaned it and installed it. I soldered the all the wires to the existing wires and tried to start the bike and BOOM! the bike starts very easily from cold, also with the kickstart even with the small lithium battery i deemed as too small.
Also the kickstarting is now way easier and I dont need to asssist with electrical start.

Then I measured the voltage at the battery and the bike was charging up to 14.6V when revved. Looks like I found the problem!

I started the bike several times enjoying the easy start over the last days and was really happy with how it turned out.

Yesterday unfortunately I measured again and the bike was again not charging :-( measured again for continuity between the three prongs of the stator and I had that between 2 prongs :-(
What could cause this to happen again? Maybe I am unlucky and the spare generator is also broken?But why did it work for a short time and supply the battery with the right amperage?