Yam RD "Blue Dream"- Ride,Maintain,Tune

2_DONE_THE_TON

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Hey guys!

It took my 1 year of hard work to restore my RD 250 built 1979.Now i´m in the middle of riding and maintaining it.This project had a steep learning curve and i will keep the curve steep :)

The bike is now stock 250 besides a slight overbore.Carbs and intake fully stock.Pretty much any seal or gasket was replaced.
Carbs were meticulously cleaned.
She rides great,pulls like a diesel truck but I miss some kind of an "edge" 8)

For the next months i plan this:

Keep stock 28MM Carbs
-carb mod: R5 emulsion tube exchange
Y boot plus K+N air filter

For the winter i plan on doing this:

-350 conversion
Cylinders and heads already sit on my shelf
oil pump cog, primary cog and 350 clutch basket still need to get bought by me

-mild porting

-chambers-probably the ones off the LC,1WWT or 31K exhaust


this is how she looks/runs now:

https://www.youtube.com/watch?v=lKnMbaRlcoM
 

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2_DONE_THE_TON

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for the carb mod:

i need to replace the stock emulsion tubes with the ones off the Yamaha R5.left you can see the stock emulsion tube,right the one of the R5.
these are pics of a RD tuning website.

to make it work properly i need to drill out 2MM of the air vent of the carb,blue arrow in third pic.
 

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2_DONE_THE_TON

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carb mod2:Y boot with K+N air filter

do you guys prefer K+N or Uni for this mod?heard that the Uni hates getting in touch with gasoline....
 

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teazer

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Q: Why?

It's part of the so called Dave F carb mod and makes no sense. R5 was piston ported and needed to be leaned out at small to mid throttle openings - much more than an RD with reed valves.

The whole change is designed to change teh amount of fuel at different throttle openings and loads. Does your engine need those changes and is that teh best way to do it?

On the 400, Yamaha changed to a taller spray nozzle to richen up high RPM fueling and it's a 284 series IIRC. That changes teh fuel slope. ON a stock bike with stock exhaust, try it on a dyno and if necessary change jets but don't just follow the crowd.
 

2_DONE_THE_TON

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hey teazer!thanks for chiming in!

so you mean the r5 emulsion mod is not useful performance wise?

i want to make the Y boot mod not only performance wise,of course i will need to rejet but the stock intake box with the rubber boots hinder any work on the carbs.

if i stick to stock carb emulsion tubes and y boot plus rejetting,will this increase performance?
 

jpmobius

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I'm in the Teazer camp on the emulsion tube swap. You should be able to have it running fine with the stock ones, adjusting jets and needle height to accommodate the air cleaner. Good additional power can be had with some good pipes and cylinder head mods without compromising reliability. I would tune the carbs as needed to suite the air cleaner and leave it at that until you convert to the bigger bore.
 

2_DONE_THE_TON

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jpmobius said:
I'm in the Teazer camp on the emulsion tube swap. You should be able to have it running fine with the stock ones, adjusting jets and needle height to accommodate the air cleaner. Good additional power can be had with some good pipes and cylinder head mods without compromising reliability. I would tune the carbs as needed to suite the air cleaner and leave it at that until you convert to the bigger bore.
hey mobius!
the r5 emulsion mod was anyways not really my pair of shoes,drilling around on the stock carbs is in my view not the way to go.
sorry for asking again but would you recommend the y boot plus k+n filter as a first mod?
i will need to rejet so i would buy 2 sizes bigger and 2 sizes smaller than my stock 115 mains.i would start rich then work my way down.
will i need the rejet the idle jets too?


my 350 haeds already seem to be modified.i will send pics this evening!

thanks in advance!!
 

Tune-A-Fish

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Not sure where you will buy the Y-Boot and filter, but HVC is $24 apart from K$N and UNI so no cost issue on either at $100><

The K$N is probably better up front and yes the UNI will become a wet sock if you clean it in gasoline. I have a minute of experiance with both and can say for sure that if you clean them often the UNI will out perform the K$N due to the fact you will begin to see the cotton break down and holes will form as it does, if you ever use air on a K$N you have blown fibers away that used to filter air, in saying that you also will ingest fibers with dirt on them over time... the UNI however will only take a cleaning for so long and the thing just starts to come apart at the seams (with warning). I would go to a track day and without asking any questions at first look and see what is being ran by the privateers... no sponsor for filters will show you what the guys who pay to play run.

IMO... Nothing is better than foam and oil :eek:

Link to an awesome shop for parts: if you haven't been already 8)
http://www.hvccycle.net/y-boot-air-filter-k-n/
 

jpmobius

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I've been using K&Ns. I like this conical one better than the straight - much easier to install and remove. Part # RC-2600 for the stock y-boot on the RDs. A section cut from a common size food can makes a perfect coupler.
 

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jpmobius

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And just FYI, I have found the R-5 emulsion tubes to work pretty well with some pipes/port/etc combinations, but can't recall which ones unfortunately.

Regarding the oil pump drive for the 350cc cylinders, you do not have to change anything. In the US, 1973-75 250cc RDs had a higher ratio primary gear set to work with the smaller output if the 250 compared to the 350. You can certainly put 350 parts in your bike, but you will need the 350cc drive gear for the crankshaft and the matching clutch basket with the corresponding gear. Then you will of course need the matching oil pump drive gear. As far as I know, there is no difference between the 250 and 350 pumps; There is enough adjustment through shimming the pumps to accommodate the difference in engine displacement. You will no doubt be pleased to learn that putting a 250 gear set in a 350 was a popular performance modification back in the day, though from a practical perspective you can achieve the same thing by changing sprockets in the final drive.
 

2_DONE_THE_TON

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Re: Yam RD &quot;Blue Dream&quot;- Ride,Maintain,Tune

Thanks mobius for the info!

So to put it in a nutshell i will need:
350 cc clutch basket
350cc drive gear
350cc oil pump drive gear

Do you know if these parts are marked somehow so i can be sure when i buy these parts that these are from the right model...the 250cc version is 2R8 and i think that 350cc is 2R9....do the parts somehow have punch marks or something?

As for my first mod the Y Boot:
How would you go about rejetting?
I have now 115 stock main and 25 idle now.
I guess start rich with 125 then work my way down,how can i see that i need to go leaner,plug chops or how do i 'feel' running too rich?

Thanks for your input!
 

davedogg

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Here's some instructions on the carb mod. Should help answer your questions.

http://www.2strokeworld.com/manuals/Dave_F_W-Pictures.pdf
 

teazer

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The Dave F/Dale A mod has been around for years and no one has yet come up with an explanation of what it does or how it helps. No data on A:F ratios stock versus with the mod.

What problem in the fuel slope is it trying to fix?

AFAIK, the 350 has faster spinning transmission to reduce loads on the transmission gears and it is way easier to just gear it differently at the rear wheel. For years people swapped 350 top ends onto 250s and had no issues with the trans or oil delivery. I race a 250 TZ for years with a 350 or TZ750 top end and no changes to the bottom end at all. Gearing was different than on a full 350 but that's not an issue to work out.

I never investigated it, but is the 350 set up to deliver more oil or just the same as a 250? If it's the same, there's no need to change anything.
 

jpmobius

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Like I said, I don't think you need to change anything. I do not have the part numbers handy, but do not believe they are indicated on the individual parts. The difference is in the number of gear teeth. You can pull off your right side case and count the teeth on your primary and oil pump drive gears. The crank gear will have more teeth, and the clutch basket and oil pump drive will have fewer teeth. There are only two "sets", one for 350's and one for 250's, and you either can't assemble mismatched parts or they are obviously are not correct.

You can estimate the oil ratio by observing how much oil you have to add to the tank compared to the fuel you use. Add or remove shims to get the desired rate of oil consumption. You should be starting out rich as hell with the new top end, so add shims to start with, and then just remove shims to close in on your desired ratio. Not a huge difference between the 350 and 250 oil consumption anyway.
 

2_DONE_THE_TON

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Thank you guys for the insight!

Interesting what teazer wrote about putting the 350 top end on the 250bottom.
What i read is that the clutch is the problem.slipping clutch.
Maybe the guy who made the website didnt really know what he was doing :)

Mobius what is your estimation on this issue?should i buy the 350 specific parts or just run with the 250 bottom end?

The last few rides i found an annoying issue with my RD.
The right plug tends to foul.the carbs are now in perfect tune,she really purrs and the plugs look really good when ridden hard,but when i let her sit for 1-2 days the starting takes longer and she tends to smoke way more after starting then when she has been ridden.
Today the right exhaust smoked more then the left one.
After a few minutes of riding it the problem dissapears (one can even hear the fowl of plugs when the motor is cold).
Should i worry or is this just a classic RD phenomenon?

FYI the issue with the motor dying when i braked from higher rpms was just a carb tuning issue as mobius stated earlier and is sorted :)
 

jpmobius

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The 250 and 350 clutches are the same on US '73-'75 models, just the basket is different, and that is just because the drive gear is different - the basket itself is the same. That said, the torque offered to the 250 basket will be increased compared to the 350 because of the higher gear ratio, so potentially there could be an increased potential for slipping, though I have not had this experience myself, and I have run many 250 primary sets with 350 top ends. That is not as valuable advice as it may sound as many of those engines were far from stock and required much stronger clutches. I would keep all the 250 components like you have them and go to aftermarket drive plates and/or springs if you have a problem. Trans oil can have a big impact. I am using non-synthetic Shell Rotella diesel oil because it seems to make the transmission shift more smoothly, but the clutches seem to like it as well.
 

2_DONE_THE_TON

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Re: Yam RD &quot;Blue Dream&quot;- Ride,Maintain,Tune

Nice mobius that will save me a lit of money,if i run into clutch slipping i can still change the parts anyways.
Do you have an idea what the fowling problem could cause i stated i my last comment?
 

2_DONE_THE_TON

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Re: Yam RD &quot;Blue Dream&quot;- Ride,Maintain,Tune

Hey guys!long time no hear had a blast the last days riding my RD last week i pulled of the heads to take a look at the cylinder walls and pistons.
All looked good besides the left cyl had a few scratches,it was kinda hard to get a good shot but it was not terrible grooved just slight scratches.should i be worried?
The pistons looked good,they had slight coal.

I gave the carbs a little clean out to,the little air drilling of the right carb was blocked.
 

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Tune-A-Fish

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Looks like some dirt got on the rings, the scrubbing above the smoke ring right where the scratches are shows something was/is riding the ring? suggest pulling that jug being that your that far in... just to inspect the rings.

Also, what are you running for burn oil... seems a little wet, is it drooling oil?
 

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