collapse

www.dimecitycycles.com

www.cognitomoto.com

https://www.townmoto.com/collections/vanson-leathers

www.speedmotoco.com

www.CITYLIMITMOTO.com

www.jadusmotorcycleparts.com

www.lostapostlejewelry.com

www.sparckmoto.com

www.pistonsociety.com


Author Topic: Yam RD "Blue Dream"- Ride,Maintain,Tune  (Read 53333 times)

Offline TranceMachineVienna

  • DTT SUPPORTER
  • *
  • DTT BOTM WINNER
  • *
  • Posts: 1961
Re: Yam RD "Blue Dream"- Ride,Maintain,Tune
« Reply #60 on: Jul 28, 2015, 09:53:55 »
+1 on getting the heads squished, o-ringed, and yz125 reed petals. I have that on my 350 and it the tits.

by yz125 reed petals you mean replacing the whole reed cage of the 350 with them dont you?
what does this change performance wise?
there are these v force membranes out there too,but terribly expensive!

Offline Tune-A-Fish©

  • DTT SUPPORTER
  • *
  • Posts: 6844
  • BOTM LOSER Proudly Deplorable
Re: Yam RD "Blue Dream"- Ride,Maintain,Tune
« Reply #61 on: Jul 28, 2015, 10:48:24 »
I won't try and answer for Mobi... But We ran those V-Force reeds in our bikes before the 4-Stroke took over and they are/were an improvement over stock reeds, much better power curve, still a big hit when it comes on and when you stay in the pipe the reeds respond to throttle input very well.

Then it all changed with 4-strokes, we had to beef up radiators, add better impellers to the water pumps, dig out the valve seats and replace most of the top end, squish and widen the intake ports all in an effort to run cooler and build in some HP to match the torque... Can you say "Parts Unlimited" LOL!... ruined MX IMO... now you have very few riders with the training or money to compete at the very top, even with everyone under the top ten being faster than most brains can even process the obstacles in front of them. Everything leads back to video games mang :o
"I didn't come here and I ain't leavin"  Willie Nelson

"love hard, live fast, die fun" Kacey Musgraves

"Like a Wreckin Ball!" Eric Church

Offline jpmobius

  • DTT BOTM WINNER
  • *
  • Posts: 1229
  • where does this go?
Re: Yam RD "Blue Dream"- Ride,Maintain,Tune
« Reply #62 on: Jul 28, 2015, 11:36:13 »
For me, replacing the reed cages falls into the "I am willing to spend unlimited amounts of money on my bike" category.  There are benefits, but they are expensive, and need to go hand in hand with a lot of other expensive changes to realize them. 

I was suggesting using the petals only on your stock cage blocks.  The YZ reeds have 3 petals, but the petals are the same size as the RD's, so you can cut off one and throw it away and install the remaining two just like stock.  It will be a minor change to the engine - seemingly more valuable to some combinations than to others.  Likewise to banshee crossover tubes, enlarged crossover tube reservoirs, and carb/reed spacers.  All can effect how the bike drives but I am not sure that any of these changes actually make more power.  However if the combination you use gets you better drive off of corners, or makes the bike more pleasant to drive, the benefits are obvious.

In your pic, the left cylinder is the style of early US 250/350's with the early ring copper gasket.  Very hard to seal on stock good running engines - impossible to seal on high output motors.  However, it is the best style for modified heads because you can machine the head with a step that makes it sit down inside the recess previously used for the copper gasket.  It is then a simple matter to cut a groove for an o-ring, and then cut the center for the squish you want and combustion chamber volume.  The benefit here is that the interlocking steps force the head to be exactly centered over the cylinder, or more importantly the piston.  Your new squish area will be very close to the piston at TDC, (.035"-.040", or 0.9 to 1.0 mm). Because the piston is crowned, and the stock head arrangement is exceptionally sloppy and you can easily install the head considerably off center, the squish can be way too thin on one side and way to wide on the other.  The alternative is to machine a centering tool to perfectly center the head on the bore, and install some alignment pins to locate the head.  The only downside is that the early heads are thin and prone to cracking, but my opinion is that this is primarily caused by the gasket design and over torquing.  If you start with good condition heads you should be fine.

The right cylinder is the later style 250/400 scheme which has flat topped cylinders and uses the gasket you are familiar with.  This is a huge improvement over the early style as tightening the head does not bend the head over the gasket causing it to leak and crack.  With care and copper gasket spray you can reliably get heads to seal, but this is no match for o-rings.  You need to center and pin these heads for optimal performance. 

I do not have a picture of altered early heads, but I have an aftermarket RD o-ring head sitting here.  It has a good squish and chamber, but has not been fitted to an engine yet and has no alignment pins or other engine specific modifications.  This head was made by Ottoco before they sold to HVC.  It is a 350 head without the step so it can not be used on a stock 350 cylinder.
« Last Edit: Jul 28, 2015, 11:42:23 by jpmobius »
Mobius


On a long enough timeline, the survival rate for everyone drops to zero.

1973 RD350 Yamaha build  http://www.dotheton.com/forum/index.php?topic=66498.0

Offline TranceMachineVienna

  • DTT SUPPORTER
  • *
  • DTT BOTM WINNER
  • *
  • Posts: 1961
Re: Yam RD "Blue Dream"- Ride,Maintain,Tune
« Reply #63 on: Jul 28, 2015, 11:44:08 »
I guess this is again a question of budget.the vforce 4 reeds cost about 180 euros in europe a piece....crazy!
If these yz 125 petals are cheaper and bring reasonable improvemenr i will buy them.

Offline Tune-A-Fish©

  • DTT SUPPORTER
  • *
  • Posts: 6844
  • BOTM LOSER Proudly Deplorable
Re: Yam RD "Blue Dream"- Ride,Maintain,Tune
« Reply #64 on: Jul 28, 2015, 11:51:58 »
For me, replacing the reed cages falls into the "I am willing to spend unlimited amounts of money on my bike" category.  There are benefits, but they are expensive, and need to go hand in hand with a lot of other expensive changes to realize them. 



Although I don't disagree, I would say that the money spent above the base plate gasket is minor pocket change in comparison to below and we are spending for the expansion chambers already. Machine work if well thought out to add a grove and align the squish with the world seems basic bucks well spent and well a little "mild" buzzing with a porting guru shunt cost the moon or you need to buy more drinks at the pub :o mang...

I guess it boils down to what you said about driveability (performance) and what you want as a reliable but racy sport classic. As for the over rev... put a dollar sign on your tach where the box should come on?? (smile face)
"I didn't come here and I ain't leavin"  Willie Nelson

"love hard, live fast, die fun" Kacey Musgraves

"Like a Wreckin Ball!" Eric Church

Offline Tune-A-Fish©

  • DTT SUPPORTER
  • *
  • Posts: 6844
  • BOTM LOSER Proudly Deplorable
Re: Yam RD "Blue Dream"- Ride,Maintain,Tune
« Reply #65 on: Jul 28, 2015, 11:57:28 »
I guess this is again a question of budget.the vforce 4 reeds cost about 180 euros in europe a piece....crazy!
If these yz 125 petals are cheaper and bring reasonable improvemenr i will buy them.

If you were in the US I would give you some carbon petals off V-force cages to try, but seems if the budget is this tiny one failure would set back the project a millennium LOL... eBay?

Just kidding of course :o
"I didn't come here and I ain't leavin"  Willie Nelson

"love hard, live fast, die fun" Kacey Musgraves

"Like a Wreckin Ball!" Eric Church

Offline jpmobius

  • DTT BOTM WINNER
  • *
  • Posts: 1229
  • where does this go?
Re: Yam RD "Blue Dream"- Ride,Maintain,Tune
« Reply #66 on: Jul 28, 2015, 12:17:59 »
As for the over rev... put a dollar sign on your tach where the box should come on?? (smile face)

Indeed!  Maybe that is a good summary.  While maybe not technically true, in my experience, everything you do hunting for more power out of a 2 stroke ends up with more revs.  Oh you may decide to not exceed the red line Du Jour, but inevitably your creation will spend a great deal more time knocking on the door.  THAT ultimately works out to expensive in my experience!
Mobius


On a long enough timeline, the survival rate for everyone drops to zero.

1973 RD350 Yamaha build  http://www.dotheton.com/forum/index.php?topic=66498.0

Offline jpmobius

  • DTT BOTM WINNER
  • *
  • Posts: 1229
  • where does this go?
Re: Yam RD "Blue Dream"- Ride,Maintain,Tune
« Reply #67 on: Jul 28, 2015, 12:41:51 »
I would say that the money spent above the base plate gasket is minor pocket change in comparison to below and we are spending for the expansion chambers already. Machine work if well thought out to add a grove and align the squish with the world seems basic bucks well spent and well a little "mild" buzzing with a porting guru shunt cost the moon or you need to buy more drinks at the pub :o mang...
Agreed.  I probably should have been a bit more clear - from a "bang for the buck" perspective, chambers, air cleaner, and the described head work take you a long way while keeping a nice, rideable and reliable but faster motorcycle.  I am promoting stopping at this point.  You can add some port work to that, but that is a sure enough slippery slope so I place it on the other side of this equation.  You can fool around with some inexpensive intake bits like the reeds, spacers etc for small money and slight performance changes.  Past this point, the money starts to grow dramatically, but more importantly the time and talent required to realize the benefit.  And there are invariably big trade-offs in practicality both day to day and long term.  The lifespan of air cooled Rd motors fall off rather precipitously once you start widening the ports and upping the output past the just chambers and heads point, and for me that factors heavily into the cost.  If the engine lasts half as long - and that is not an unrealistic expectation - it DOUBLES the original cost that at the time may not have seemed so high.  On the track, it is just the cost of doing business, but on a street bike it make a big impact.
Mobius


On a long enough timeline, the survival rate for everyone drops to zero.

1973 RD350 Yamaha build  http://www.dotheton.com/forum/index.php?topic=66498.0

Offline Tune-A-Fish©

  • DTT SUPPORTER
  • *
  • Posts: 6844
  • BOTM LOSER Proudly Deplorable
Re: Yam RD "Blue Dream"- Ride,Maintain,Tune
« Reply #68 on: Jul 28, 2015, 12:44:18 »
See how fun this can be 8)
"I didn't come here and I ain't leavin"  Willie Nelson

"love hard, live fast, die fun" Kacey Musgraves

"Like a Wreckin Ball!" Eric Church

Offline TranceMachineVienna

  • DTT SUPPORTER
  • *
  • DTT BOTM WINNER
  • *
  • Posts: 1961
Re: Yam RD "Blue Dream"- Ride,Maintain,Tune
« Reply #69 on: Jul 28, 2015, 16:47:47 »
Thank you guys for the interesting insight you give me!

My plan is:
250 configuration:
DG chambers
KN filter plus carb work

In winter i will do:
350 conversion
Squish band mod
O ring mod
Reeds (costs :-)?)
Crank rebuild

How long do yoy guys run your cranks?do you wait till it breaks :-) or do you have certain intervala to check them?

It will be hard to find someone in austria do the trueing.
Theres a guy in schwechat near vienna but he mainly build speedway cranks for rich russians so he wknt be that motivated to do that poor students crank :-)