Yamaha RD Startup
- Thread starter 2_DONE_THE_TON
- Start date
Right. Tweaking Bad! If you have everything totally stock - porting, pipes, cylinder heads, carbs, intake and air cleaner, and stock ignition timing, you can be pretty confident with the stock jets, at least to get going. The concern is to run the motor too lean, and getting it too hot which expands the piston(s) which makes them too tight in the bore = partial (or worse) seizure.
So the notion is to err on the fuel rich side and plenty of oil until things are known to be sorted out. You have things very easy as Yamaha has already done this, so all you have to worry about is compensating for any modifications you have made or variances in production. Assuming on your first real test ride you intend to break in the motor, you will be loading the motor briefly enough that you should have no worries. You can always start with rich jetting to be sure, but if all stock, why would the stock jets not be ok? I can not see the intake side of the carbs in your pics, but if stock, I'd start with the stock jets. If altered, go with bigger jets.
It is sort of like excess oil: The only down side is fouled spark plugs which are cheap. Too little oil and seizure. Not so cheap
Same thing with excess fuel. The only down side is fouled spark plugs which are cheap. Too little fuel, too much heat and seizure. Not so cheap.
And likely you are not going to need a zillion spark plugs. I always start very rich on fuel and oil, and usually get the motor broken in, jetted close enough to actually run hard with the plugs I started it with. Often enough the first new plugs go in when I plan to do my first plug chop.
When in doubt, always jet rich. Gasoline engines are principally cooled by the gasoline itself. In order to burn, the liquid gasoline must be converted to a gas. This is called the heat of vaporization and takes substantial energy to do, and the energy comes in the form of heat from the reaction itself. Consider an engine running with a fuel to air ratio richer than ideal. There is a surplus of fuel to vaporize and thus keeping the engine cool is easy. As the ratio of fuel to air becomes leaner and closer to perfect, the more energy (power) is produced by the chemical reaction and with it more heat. At the same time, there is less fuel to vaporize to remove heat. Once there is just a little too little fuel, there is still plenty of chemical reaction heat, but no longer enough vaporizing fuel to consume excess heat, and the engines mechanical cooling system must suffice. Since this system has a fairly finite limit, it is easy to see that as soon as the liquid gasoline stops being supplied in sufficient quantities to keep temperatures at bay, the whole thing will heat up more and more with every revolution. So too lean motors get hot rather quickly and often dramatically. TWEAK!
As to when to do plug chops, anytime after the motor is broken in is fine. Plug chops can be likened to taking a snapshot of your engine while it is making maximum power. Maximum power comes with making maximum heat. Guess what happens if it is too lean!
So the notion is to err on the fuel rich side and plenty of oil until things are known to be sorted out. You have things very easy as Yamaha has already done this, so all you have to worry about is compensating for any modifications you have made or variances in production. Assuming on your first real test ride you intend to break in the motor, you will be loading the motor briefly enough that you should have no worries. You can always start with rich jetting to be sure, but if all stock, why would the stock jets not be ok? I can not see the intake side of the carbs in your pics, but if stock, I'd start with the stock jets. If altered, go with bigger jets.
It is sort of like excess oil: The only down side is fouled spark plugs which are cheap. Too little oil and seizure. Not so cheap
Same thing with excess fuel. The only down side is fouled spark plugs which are cheap. Too little fuel, too much heat and seizure. Not so cheap.
And likely you are not going to need a zillion spark plugs. I always start very rich on fuel and oil, and usually get the motor broken in, jetted close enough to actually run hard with the plugs I started it with. Often enough the first new plugs go in when I plan to do my first plug chop.
When in doubt, always jet rich. Gasoline engines are principally cooled by the gasoline itself. In order to burn, the liquid gasoline must be converted to a gas. This is called the heat of vaporization and takes substantial energy to do, and the energy comes in the form of heat from the reaction itself. Consider an engine running with a fuel to air ratio richer than ideal. There is a surplus of fuel to vaporize and thus keeping the engine cool is easy. As the ratio of fuel to air becomes leaner and closer to perfect, the more energy (power) is produced by the chemical reaction and with it more heat. At the same time, there is less fuel to vaporize to remove heat. Once there is just a little too little fuel, there is still plenty of chemical reaction heat, but no longer enough vaporizing fuel to consume excess heat, and the engines mechanical cooling system must suffice. Since this system has a fairly finite limit, it is easy to see that as soon as the liquid gasoline stops being supplied in sufficient quantities to keep temperatures at bay, the whole thing will heat up more and more with every revolution. So too lean motors get hot rather quickly and often dramatically. TWEAK!
As to when to do plug chops, anytime after the motor is broken in is fine. Plug chops can be likened to taking a snapshot of your engine while it is making maximum power. Maximum power comes with making maximum heat. Guess what happens if it is too lean!
Thank you mobius for your expertise!
Do you rev your engines up and down when you start fresh,I ask cuz i watched some first start up videos on youtube,the people rev their 2 stroke engines up and down,i guess to warm them up...is this the way to go?
I normally see this more with people starting motor that cant idle so they rev them
Do you rev your engines up and down when you start fresh,I ask cuz i watched some first start up videos on youtube,the people rev their 2 stroke engines up and down,i guess to warm them up...is this the way to go?
I normally see this more with people starting motor that cant idle so they rev them
Well, it is pretty unlikely that you will have accidentally happened on the right idle screw adjustments, so either your idle will be too high or too low. For the record, on Mikunis like yours I srew the idle screws in until they contact the slide and then about another 3/4 turn which is usually not too far off. If low, you will have to keep it running manually as you adjust the throttle stops. If high, you will need to back them off. Regardless, I generally keep blipping the throttle because I don't want to let the engine remain at any one speed for long until it is broken in. Also keeping manual control keeps it from dying until it is warm enough to run by itself. I probably rev it to 2 or 3 k from idle more or less constantly and maybe up to 5k a couple of times while getting it up to FULL operating temperature and then shut it off and let it cool down to dead cold and check the head torque. (and anything else) I generally don't try to adjust anything except the idle stops until after break in unless the engine won't idle.
crazypj
Split personality, I fake being smart
Too much oil can be a bad thing, even with oil injection set up.
Burning oil produces heat without any further benefits.
It's unlikely to cause engine damage but I have seen exhaust systems catch fire acting like a flamethrower (wondered why every one was honking at me during a test ride ;D )
Made one hell of a mess of the chrome on customers bike
From cylinder almost all the way along silencer was purple and blue (I kinda thought it was cool)
Burning oil produces heat without any further benefits.
It's unlikely to cause engine damage but I have seen exhaust systems catch fire acting like a flamethrower (wondered why every one was honking at me during a test ride ;D )
Made one hell of a mess of the chrome on customers bike
From cylinder almost all the way along silencer was purple and blue (I kinda thought it was cool)
VICTORY!!
this week end i finally had the time to do the first start up together with two buddies!
she started pretty easily after i made same noob mistakes (forgot to close the drain screws on the carb bowls 8) ) , letting the run switch on OFF et cetera...you know the deal
and man she SMOKED!!! interestingly she smoked white....maybe it was just the light (it was late evening)
i didnt have to change the plugs once...they held up interestingly.
the video shows the process of filling the oil lines,afterwards i started her with straight gas and she smoked a lot less!
i tried not to let her run to long in one RPM range so i revved her now and then but not over 5000rpm.she idled pretty easily at around 1,500.
enjoy at around 8:00 its getting serious!
https://www.youtube.com/watch?v=cqHelcyLdLw
this week end i finally had the time to do the first start up together with two buddies!
she started pretty easily after i made same noob mistakes (forgot to close the drain screws on the carb bowls 8) ) , letting the run switch on OFF et cetera...you know the deal
and man she SMOKED!!!
interestingly she smoked white....maybe it was just the light (it was late evening)i didnt have to change the plugs once...they held up interestingly.
the video shows the process of filling the oil lines,afterwards i started her with straight gas and she smoked a lot less!
i tried not to let her run to long in one RPM range so i revved her now and then but not over 5000rpm.she idled pretty easily at around 1,500.
enjoy at around 8:00 its getting serious
!https://www.youtube.com/watch?v=cqHelcyLdLw
I love the idling sound.interestingly the motor really took long to warm up,both cylinders felt like same warmth.is there a good method to synch the two cyls besides grabbing the downpipes and feeling the pulses?
crazypj
Split personality, I fake being smart
Not really.
With the later models you could fit vacuum adaptors into 'boost bottle' ports.
Check if you have the brass screws on sides of carbs, that should allow slide sync although I think earlier models just had screw on one carb to make setting oil pump easier
With the later models you could fit vacuum adaptors into 'boost bottle' ports.
Check if you have the brass screws on sides of carbs, that should allow slide sync although I think earlier models just had screw on one carb to make setting oil pump easier
Ok.actually she sounds pretty much synched up,lets see how she rides
Ok thank you.what does line snatch mean?that the bike tends to go left or right when it should drive straight?
I replaced all the clutch pads with new oem pads since some of them were broken,the dampers are original and not replaced.
The clutch feels strong on the hand.is it possible that the clutch is tightened too strong and that this is the reason that the lever feels so hard?
I replaced all the clutch pads with new oem pads since some of them were broken,the dampers are original and not replaced.
The clutch feels strong on the hand.is it possible that the clutch is tightened too strong and that this is the reason that the lever feels so hard?
Congratulation on a successful first start up! Sounds fine in the video. Good job on showing the complete process including discovering the silly oversights - hope you have more success at avoiding them with experience than I have had!
I "sync" carbs like this by adjusting the cable adjusters on each carb. Back the idle stop screws out so they do not touch the slides and then simply adjust the two cables so both slides to just lift from fully closed at the same time. Then adjust the idle stops for whatever idle you like.
Rd's can have a very annoying characteristic of surging when decelerating. Usually this can be managed by richening the low speed mixture. If you have this issue try raising the needles one clip position (put the clip on the next lower groove). Or go up on the pilot jets, or do both. Sometimes that puts the idle mixture richer than optimal, but may be a worth while compromise for drive ability. Of course this may also create other drive ability issues - you will just have to experiment. Too much drive chain slack can amplify this issue, and no doubt a loose clutch drive hub could as well, though I can't say re-riveting it is worth while for this alone. You may be unaware of this bit of machinery as it generally has no need of interaction. The large gear attached to the back of your clutch basket is riveted on to it. Though you can not see it without disassembling it, there are slots allowing the gear to rotate a few degrees against the basket. The rivets are very tight when new, so there is no reason to notice this motion. When worn, the gear can usually be rotated back and forth easily. That big "O" ring next to the gear is the friction dampener for this mechanism. None of it is something to worry about. I always consider surging a tuning issue and try to solve it from that direction. Regardless, the deceleration surging seems to be an issue of varying severity for any particular bike, so maybe you will never have to bother with it.
I "sync" carbs like this by adjusting the cable adjusters on each carb. Back the idle stop screws out so they do not touch the slides and then simply adjust the two cables so both slides to just lift from fully closed at the same time. Then adjust the idle stops for whatever idle you like.
Rd's can have a very annoying characteristic of surging when decelerating. Usually this can be managed by richening the low speed mixture. If you have this issue try raising the needles one clip position (put the clip on the next lower groove). Or go up on the pilot jets, or do both. Sometimes that puts the idle mixture richer than optimal, but may be a worth while compromise for drive ability. Of course this may also create other drive ability issues - you will just have to experiment. Too much drive chain slack can amplify this issue, and no doubt a loose clutch drive hub could as well, though I can't say re-riveting it is worth while for this alone. You may be unaware of this bit of machinery as it generally has no need of interaction. The large gear attached to the back of your clutch basket is riveted on to it. Though you can not see it without disassembling it, there are slots allowing the gear to rotate a few degrees against the basket. The rivets are very tight when new, so there is no reason to notice this motion. When worn, the gear can usually be rotated back and forth easily. That big "O" ring next to the gear is the friction dampener for this mechanism. None of it is something to worry about. I always consider surging a tuning issue and try to solve it from that direction. Regardless, the deceleration surging seems to be an issue of varying severity for any particular bike, so maybe you will never have to bother with it.
Hey guys!
First ride out today i will post a video tomorrow everthing went fine...the bike is a blast !!! Tried to stick to jp s way of riding it in hard and it was so much fun!made a plug chop what you guys think ?
Brownish black with a lil bit of oil on the ridge.
First ride out today i will post a video tomorrow everthing went fine...the bike is a blast
!!! Tried to stick to jp s way of riding it in hard and it was so much fun!made a plug chop what you guys think ?Brownish black with a lil bit of oil on the ridge.
Attachments
Didnt red line the RD since i got new pistons and bore,but tried to shift a lot and keep the motor from staying in one rev area.these are the same plugd i used start the bike aftrr rebuildimg it,started with premix to check the oil pump.
Could this be the reason for cool plugs?excessive oil and not enough load?
Could this be the reason for cool plugs?excessive oil and not enough load?
Plug chops require brand new plugs, and the engine running reasonably well to be of much use. The idea is to take a "snapshot" of the engine while it is developing maximum horsepower. Empirical evidence shows that this is in fact very useful, but you have to be reasonably close to where you want to end up to get that information. First off, there is no value to doing plug chops to determine some pretty obvious stuff. Lots of oil for example - you don't need any help to see that! Once you get it running reasonably well, and it sounds like you do, AND you are comfortable running it wide open in top gear, you can start looking at plugs. There is one critical element to add. Before you start, make sure you have conservative spark advance and excess fuel. In other words, intentionally set your ignition timing to less advance than you expect, and install larger main jets than you expect. Otherwise, your experiments can cost you far more than the set of plugs you sacrifice to obtain the knowledge. Realize that the tuning information gleaned from spark plugs is delicate, and can not be seen without cutting apart the plug after taking the picture. Lots of car and bike manuals devote an entire page of photos of spark plugs as examples. This is totally unrelated to this subject. One pair of brand new spark plugs will be sacrificed each time. Gordon Jennings explains it far better than I ever could. You can read his explanation here: http://www.strappe.com/plugs.html. Good luck, and keep us know!
jpmobius said:
hey mobius!
today i took the RD the first time out on the streets of vienna in order to get a license to drive it legally.
when i drove it in the traffic at low speed I realised that the RD is surging just like you said.so i will try your tip and lowering the clip of the needle (raising the needle).
i will post the results as soon as i have time to do it.
So finally i got a license to run that nice thing on the street!!i´m so happy you guys were a great help!
i made a little video of the engine idling before she was getting to be prepped for paint.
i´m a little worried about the sounds coming from my engine,especially fom the crank part,maybe i´m just overly cautious like always, but maybe you can guys just watch the video an tell me what you think.
the "ringing" sound from the crank doesnt sund chaotic or anything so maybe its really just the "character of the engine".
i´m just not used to the mechanical sound of the 2Stroke engine.
The engine revs freely,everything is fine.The engine gets oil and smokes fine ;D
let me know what you guys think!
https://www.youtube.com/watch?v=SsZPVMv6RE4&feature=youtu.be
i made a little video of the engine idling before she was getting to be prepped for paint.
i´m a little worried about the sounds coming from my engine,especially fom the crank part,maybe i´m just overly cautious like always, but maybe you can guys just watch the video an tell me what you think.
the "ringing" sound from the crank doesnt sund chaotic or anything so maybe its really just the "character of the engine".
i´m just not used to the mechanical sound of the 2Stroke engine.
The engine revs freely,everything is fine.The engine gets oil and smokes fine ;D
let me know what you guys think!
https://www.youtube.com/watch?v=SsZPVMv6RE4&feature=youtu.be
runmikeyrun
Been Around the Block
I can't get the sound to work on the computer at work, but I just wanted to say she sure looks great!
Once you get used to the ring ding ding and popping of the exhaust at idle four strokes will just sound so boring in comparison lol. I had two strokes for a long time and now that I am without once I really miss the character of the exhaust.
Once you get used to the ring ding ding and popping of the exhaust at idle four strokes will just sound so boring in comparison lol. I had two strokes for a long time and now that I am without once I really miss the character of the exhaust.
