Yamaha RD Startup

it is the tongue that sets level the other tab only keeps the float from dropping too far
are you saying now that you only have 1-2mm of float movement?
what made you start to worry about the float measurement in the other direction ?
crickey you could overthink flushing a toilet ;D

I ve set my carbs with the tongue in the middle of the float to 29 MM like the manual said upside down (floats up) .
Then i flipped it like its mounted on the motor and the floats dropped down to 36mm....

Then i found that little tang that touches one of the alum 'pillars' that holds the float.

The float has more travel then 2mm....the adjustement kf the tang just 'blocked' the float from dropping down too low....
The float still has all the travel up,pressing the needle into its seat.
Or am i getting something wrong and i should not care about the upright (floats down) float lvl?

Didnt get the last sentence,sorry im not a native speaker.

Your pics are sideways. The center looks like the carb is oriented as installed. If your last picture is of the carb body inverted from the installed orientation, it is definitely wrong. The float should be much closer to the body. Typically the float is more or less horizontal when inverted, though I do not have one in front of me to check. There should be something like 30 degrees of rotation from the needle closed position to wide open, though this never actually happens during normal operation. That is not a spec, just a generalization. Maybe it is like 20 degrees. The "down" or open position has no meaningful spec except for what I have posted already. Xb is correct. Go back and review the previous posts in this thread. You are asking questions that have been thoroughly covered already. If you want to verify, post right side up pics of the carb inverted with a caliper on it to show how you are taking the measurement, and also one of your manuals description. I understand how unfamiliar things can be a bit stressful, but the mechanism is really just as simple as it looks. When the fuel is high enough in the bowl, the float closes the needle. As fuel is used out of the bowl, it cracks open just the tiny amount needed to maintain that level. It hardly moves at all. So the down position is only important mechanically. See previous post!! It is the high, fuel off position that is critical, to maintain the correct fuel height in the bowl so that has to be right. If the fuel is too high, it will be too easy for the fuel to sucked into the carb, and if too low, it will be too hard. To work correctly, the fuel level needs to be the exact same height in the bowls at all times. Carburetors may seem fussy, but they are actually pretty simple, relying on basic physics to work. Once adjusted correctly, they work amazingly well and are super reliable (plus, you can repair them yourself unlike injectors) until they get dirty from fuel deposits or come out of adjustments for some reason.

jpmobius said:

Your pics are sideways. The center looks like the carb is oriented as installed. If your last picture is of the carb body inverted from the installed orientation, it is definitely wrong. The float should be much closer to the body. Typically the float is more or less horizontal when inverted, though I do not have one in front of me to check. There should be something like 30 degrees of rotation from the needle closed position to wide open, though this never actually happens during normal operation. That is not a spec, just a generalization. Maybe it is like 20 degrees. The "down" or open position has no meaningful spec except for what I have posted already. Xb is correct. Go back and review the previous posts in this thread. You are asking questions that have been thoroughly covered already. If you want to verify, post right side up pics of the carb inverted with a caliper on it to show how you are taking the measurement, and also one of your manuals description. I understand how unfamiliar things can be a bit stressful, but the mechanism is really just as simple as it looks. When the fuel is high enough in the bowl, the float closes the needle. As fuel is used out of the bowl, it cracks open just the tiny amount needed to maintain that level. It hardly moves at all. So the down position is only important mechanically. See previous post!! It is the high, fuel off position that is critical, to maintain the correct fuel height in the bowl so that has to be right. If the fuel is too high, it will be too easy for the fuel to sucked into the carb, and if too low, it will be too hard. To work correctly, the fuel level needs to be the exact same height in the bowls at all times. Carburetors may seem fussy, but they are actually pretty simple, relying on basic physics to work. Once adjusted correctly, they work amazingly well and are super reliable (plus, you can repair them yourself unlike injectors) until they get dirty from fuel deposits or come out of adjustments for some reason.

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hey moeb!thank you so much for your patience!

made the pics you requested!

i just dont get why one adjusts the float lvl upside down (first pic from the manual even though the carbs work the other way around...

the sliding scale now shows the same MM in both directions which i now understand is wrong....

the needle needs to travel up and down to open and close the gas hole that is drilled behind the brass seat.
what i thought that it is this little pin that opens and closes...sorry for my misunderstanding but i´m still learning!

what is the purpose of the little tang shown in the fourth pic?
maybe to keep the float to open up too much and make the needle slide out and block it?

I guess i ll need to bend back that little tang to give the float more 'downmovement'.

OH MAN YOU HAVE GOT IT ALL FUCKED UP
the tab that touches the needle is what controls float height,the one in the 3rd pic it is the only thing you adjust and rarely do they even need adjusting anyway
leave the other one alone,but you need to bend it back the way it was originally, this is such a simple thing to figure out
goddammit this is stuff a child could figure out
lets hope you got the hard stuff right, inside the motor
when you are done with the bike before you ride it have a qualified mechanic inspect it for safety

To repeat, go back and re-read previous posts! I elaborated on the spring loaded pin, so you should have been able to understand that it is only a mechanical shock absorber and removed it from your work. In any event, xb is right, bend the 90 degree tang that contacts the pillar on the body back to where it was. By your pictures, the float level adjusted by the center tang is correct, though it looks very high (means it will result in a low fuel level.) to me. You say you have it set to 29 mm, and that is what it looks like. Very wrong. Your manual says 23 mm, base gasket surface to top of float. Looks to me like a 6 mm adjustment wil be just about right. Set it to 23 mm. Most of the time, the brass bracket the floats are mounted is nearly flat with only a very slight bend to adjust the float height (center tang, yours looks way overbent) and if there is a drop adjustment, it never gets adjusted, so bend yours back to 90 degrees and forget about it. To the best of my knowledge, the "the little tang in the fourth pic" only keeps the float from rotating all the way around during assembly and allowing the needle to fall out accidentally. It is just a convenience. It does not have a function in supplying fuel to the carburetor, so put it back like it was and forget about it. You adjust the level with the carb body upside down because you are letting gravity mimic the force of the floats floating in the gasoline filling the bowls. As the bowls fill with gas, the floats rise with it and push against the valve closing it. Gravity replaces this effect when upside down. Carefully re- read ,my previous posts. I did, and all this is pretty well covered. So go back an check it out.

Thank you xb for your patience!

This weekend i set the carbs to 23mm,the tang is 90 again ...i totally got this wrong sorry.

So i guess i ll finish all the stuff to start up the bike by new year(exhaust,...).
Since winter is pretty harsh here in austria in dunno if i maybe should wait till the next season starts with starting it up and running it in....
Or what you guys say?
I heard that the first couple of miles are the most important ones running the fresh bore in...bore glazing et cetera.
So starting it up and letting it run would not do the job maybe....
I m really eager to start it up finally...but wont be able to drive it the way it should be this winter...

Looks much better! Perseverance usually fixes everything.

Personally, I like to start my engines right away after assembling them. There are as many answers to the best break in process as there are motorcyclists, but here is basically what I do. I try to start my engines the day after they are complete. That is because often there is some sort of sealant that I want to set up somewhere in the assembly. I don't like to wait longer because I want to start up with as much assembly lube as possible to still be where I put it for start up. I start the engine, set the pilot screws and idle stops on the carbs and once it idles, I set the timing if not already done statically. I warm it up completely to regular operating temperature, keeping the rpms between idle and 3- 4,000 rpm and then shut it down and let it cool completely. Then check all the fasteners especially cylinder head bolts. I repeat this process a second time, then drive the bike. After warming it up first, I run it fairly hard straight away, placing strong load to the engine in all gears to about 80% of redline. Slow down, and then repeat 4 or 5 times, eventually taking the engine to redline briefly on the last pass. No constant engine speed or prolonged wide open throttle. I make absolutely certain the jetting is correct or rich if I don't know what it needs, the ignition timing carries less advance than I think it will need, and that it is getting rather a lot more oil than I think it will need. The process does not take long at all (just a few miles on the street, or one (easy-ish) lap at the track), and invariably produces good ring sealing (good power) and long life safely and reliably. So maybe you will get a clear day and get it ready for the spring!

I have built and started more engines than I will admit to in 40 years, and helped (to wildly varying affect!) more guys start their new motors than I could count. I am left with the following from that experience:

THINK!! You have a brand new engine! If everything is assembled correctly, it will start EASILY! If it does not, there is something wrong! Make sure you have good spark first, before you attempt to start it. Good spark? open the fuel tap and let the fuel bowls fill. Make sure there are no fuel leaks. Give it a minute or two. Apply the fuel enricher (choke), and your engine should start in a couple of kicks. There is no circumstance ever where you will need to do anything other than this to start a new engine if it is put together correctly. NEVER add gasoline that the carburetor didn't supply on its own. And "starting fluid" is only for people that wish to destroy a perfectly good engine (except for those living above the arctic circle or are searching for vacuum leaks). Your new motor should fire right up like starting your car when you go to work in the morning. If it does not, figure out why!

I routinely fire new engines for the first time in front of clients. They ALWAYS start more or less instantly, unless I leave my brain at home (which seems to happen with ever increasing frequency!).

Get that thing started and run in! Finish up all your bike's details while waiting for the snow to melt!

Oh man you just re-motivated me again ^^.spent so much time tearing it down,refurbishing stuff et cetera and now i wanma finally fire it up.

I just ordered a little supply tank in which i will fill in premix (1:20) when i start it up when i m finished in a few weeks,unfortunately i doing this besides my job and university and diploma...so without that i would have been done months ago .

Some months ago i watched a mechanic who races rd' s on the track first time starting his newly rebuilt engine.
The engine didnt start easily,he fiddled around on the idle screws then again didnt start then he used starting fluid ()...then it started....and man it smoked heavily (he ran just premix).and then he rode it hard around the block.
Maybe his motor was just highly modified (he had LC pipes on and different jetting settings).

He told me that he always fires the motors up with no air filter or airbox connected when starting first time....is that the way to go?
Isnt that harmful to the motor?

What i ve done is that i put everything back to stock.
Mains were 160 ,put them back to 115's (stock).
I will start with the stock settings of idle and air screws.

So setting the idle screw on each carb is clear to me (feeling the pulses of the exhaust and adjusting the motor to idle around 2000rpm) but when do you mess with the air screws?

How do i check the spark on my bike?its a cdi (RD 250F).is there way to check the spark without kicking it over?

Fuel leakage will be tested this week.

I wouldn't listen to anything someone that uses starting fluid said. No reason whatever not to have the airbox, filter, etc in place when starting. If it is put together properly, it will start. Filters are vastly more important to 2 strokes for obvious reasons. Most of my engines have never seen a single breath of unfiltered air, the exception is when I am trouble shooting something that requires the engine to be running and the box or filter is in the way.

Just set the pilot air screws to factory spec. 1-1/4 turns out probably. You can tune these after break in when you set everything up for drive ability.

it should start 1st or second kick every motor i have ever rebuilt has
you gotta be some kind of supreme idiot to use starting fluid for starting, any motorcycle engine,EVER

Yes this is exactly what i thought...effin with the air supply of a 2 stroke is dangerous especially with a freshly rebuilt motor.

Any idea how to check spark?
On my kz i would just unscrew the spark plug leave it plugged in with the spark plug holder and hold the body of the plug against the fins of the motor then use the starter and boom i have spark or not.
So its kinda hard to do this on this kickstart only CDI bike...

edit:

just found this:what you think about that tool?

http://yambits.co.uk/rd250f-spark-plug-ignition-tester-p-36502.html

There is no way to test your ignition without kicking the bike over or pushing it in gear. That tester would work. I use this sort of tester. It has an adjustable gap so I can see if it jumps 3mm or 6mm or 9mm or whatever and that gives a good indication of spark voltage.

http://www.autozone.com/test-scan-and-specialty-tools/ignition-tester/great-neck-adjustable-ignition-spark-tester/10257_0_0/

I have watched too many racers over the years who have no idea what they are doing. There is rarely a need to use starting fluid. Just hook up a tank of some sort (be safe and have a fire extinguisher and friend handy to use it) and fire it up - outside of course

Thanks teazer!
Then i will get that indicator!
How would you go about testing the spark on that RD.

My guess would be testing one spark plug after the other,leaving the one i do not test screwed in.
Or would you unscrew the other one too?i guess the best would be to have two of these indicators testing both cyl at one time...

Then i would kick the bike over...what kind of sparking can i suspect to happen?i guess it will just shortly spark since the bike will not engage completely in ignition.

by all means do a bunch of extra work that is unnecessary,perhaps you should hook it up to the christmas tree lights as well
fer fuks sakes why do you insist on making so much extra work on everything :-\
JUST START IT !!

Do we detect a cultural difference here?

Ryan, A spark tester is a cheap and useful tool. I keep 3 here for testing triples. You have single coil feeding both plugs IIRC so use two of those and kick the motor over. You should see a nice blue spark in both sides at the same time. If the spark is weak and yellow, something isn't right or you are not kicking hard enough.

common sense,i actually thought the yerpeons had more, hope is lost worldwide it seams :'(

The check you performed on your KZ will be fine. The primary value of fooling around with old bikes is their simplicity. Does it spark? If yes, then you are done with that. It is true that some ignitions either have a pitifully weak or non existent spark when rolled over by hand, but if the spark was not robust when kicked, how would it ever start? Electric starters generally don't spin the motor any faster than a kick. Easiest thing is to just grab a spare plug, put one of the plug wires on it, rest it on a chassis ground (cyl head) and spin the motor - ignition on. Got spark? check the other cylinder and move on!

I am pretty thorough preparing to start a new motor for the first time, but once in a while something is wrong, of course this can not occur unless there is an audience present! If it does not fire on 3 or 4 kicks, I stop trying and find the problem. I check for spark (see above, fast and easy). If I have spark, I check for fuel. Usually pull off a fuel line from the petcock and make sure it has put fuel into the fuel bowels. Make sure it is not sucking air from somewhere like the inricher connector hose between the carbs or the oil injector lines getting left off. It is ALWAYS something horrifyingly embarrassing, like forgot to turn the key on, put gas in the tank, left the plug wires off etc, etc. So much for being thorough!

RD's really do start very easily. If you have spark, and the fuel bowels are full of pre-mix, there is very little to go wrong!

Thanks teazer and jpmoebius!

Xb why do you even waste your precious time to write those postings?i just cant see the point trying to scream stuff trough your keyboard.

I tend to ask questions and learn from people who are more experienced then me.

Ryan Stecken said:

Thanks teazer and jpmoebius!

Xb why do you even waste your precious time to write those postings?i just cant see the point trying to scream stuff trough your keyboard.

I tend to ask questions and learn from people who are more experienced then me.

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He's a grumpy dude. Don't worry about it. But in all honesty, you need to be doing as much reading as you can. Simply asking questions in this thread isn't enough, and many of your questions have been answered hundreds of times elsewhere. Do some searching around the forum, binge read some build threads,