Bring the power curve down the rmp range

[waktaylor]

wow I've been working on my dayona for about a year and finally assembled it. Today I jetted around about 10 miles and got the feel for these old 2 strokes. No power then at 5500 rpms it moves forward in time to aboit 8500 rpms. I was easy on it for a couple miles for break in but its mine so if I break it you don't care anyway. Couldn't help myself.
Also vforce 3 reeds

So, how do I bring some power a bit lower in the rpm range? I habe mild port job by clough and vm30s with 280 mains per my favorite person CHUCK.  Set the timing at about 1.9mm BTD with points. May switch to dyna S since I have it.

Maybe some longer intake runners to pump some more air at lower rpms versus the bigaz pod filters i have currently.

Also habe rhe team scream crossover bottle on the intake.

[Organicjedi]

Down gearing the sprockets help to bring more grunt down low.

[Dvsrd]

An ignition setup with an actual timing curve may help the low/mid range power, by allowing more advance at just. midrange rpm. Either a Zeeltronic box or HPI or Vape with built in variable timing. If the heads are stock, modifying them may help as well. Or modified exhaust. Adding an inch or two to the headpipes is something you could try also.
I get a little confused though, why did you have your cylinders. ported and 30 mm carbs fitted if low end pull is important for you?

[waktaylor]

I follow you on the ignition curve tuning and will get into that over the next few weeks.

The engine ate the right side piston 2 times in a few miles for the previous owner. I found that they had the ignition set at 2.4mm BTDC and the right piston was EVEN further advanced so it was detonating.

The head was cut in two and machined by Scott Clough when he did the mild porting job; this and the VM30 carbs was done to remedy the strange stuff the Daytona had from factory and the melted piston had damaged the cylinder some. You can might not be able to see in my crappy picture that it has expansion pipes already. To clear up your confusion, I had no desire for a torque monster 2 stroke unicorn, just looking for what works to move the power back down a little.

Maybe drop the VM30s for 26 or 28mm?

An ignition setup with an actual timing curve may help the low/mid range power, by allowing more advance at just. midrange rpm. Either a Zeeltronic box or HPI or Vape with built in variable timing. If the heads are stock, modifying them may help as well. Or modified exhaust. Adding an inch or two to the headpipes is something you could try also.
I get a little confused though, why did you have your cylinders. ported and 30 mm carbs fitted if low end pull is important for you?

[waktaylor]

May look into this after I address the variable timing. I need to stretch it out to see what my top end feels like before I decide to regear.

Down gearing the sprockets help to bring more grunt down low.

[Barrie]

Simple, lengthen your exhaust , it will come on pipe earlier.

[m in sc]

those look like old school specII pipes.  they can make lower end power but also rev to the moon.

have you tried richening the needle a clip? you have 10 miles on it, no way the tuning is dialed in yet. throw soem fuel at it down low. if it gets worse, go the other way.

  Last 400 i had had  VM34s on it and it was a tractor, and ran a dyna ignition (so no curve) with denco chambers .

[Jspooner]

Once you start modifying with pipes, porting, carbs, etc. its a guarantee you will loose something somewhere in the power delivery department and thats usually going to be in the low end area unless you build the motor with that in mind from the get go. As previously stated, lower gearing will help, smaller carbs will help or even staying with 30s but going to TMs will help. Your pipes look like old school Spec IIs and could be your problem if thats what they are. Get some modern pipes, that will help but not totally, you could always go back to the stock pipes, that will help if you want low end. The DynaS will not change how it runs and for sure will not change the power delivery all it will do is eliminate the points, also, your problem could be all in the needle jet/jet needle combination and where you have it set at. Maybe Chuck will chime in soon and give you some different or better ideas. I run a motor with a TZ top end and 38MM lectrons on the street and it is a torque monster with gobs of low end and midrange, so it can be done with all the right stuff.

[SUPERTUNE]

New Spec2 F1-pipes are better on the bottom than the older version Spec2's you have.
Gearing change is a must if your trying to run stock gearing as the Daytona 2V0 cylinders have some very low port emission porting and ran higher gearing than the STD 1A1 RD400's.
Daytona came stock with 17/37 and the 1A1 were 17/38.
First thing would be a 16T front, then a 39T-40T in the rear all depending on how much highway riding you want to do?
My overported Yellow Screamer still can cruise 70-75 mph even with 16/42 gearing.
I've only stayed with new VM28's, never tried VM26's on a RD?
If running a 90 sized rear tire...it will want the lower gearing too.
Chuck

[Brad-Man]

How about PWK28's?

Probably get better gas mileage too.

[waktaylor]

Thanks, everyone. Yes it sounds like I have some dialing in to do. First 2 stroke street bike for me so didn't know what to expect.

Anyone know if the Zeeltronic Programmable CDI (link below) will work with the dyna S pickups?

Im ordering new sprockets today and a 520 chain so Im sure I will be much more happy since the stock gearing is tall.

New pipes are not really in the budget at the moment. Im really debating putting stock back on the pipes are VERY loud. Or course the trade off may be worth it.


https://www.economycycle.com/product-category/yamaha-rd250350400r5ds6ds7-parts/electrical-ignitions-lighting/ignition/cdi-ignition-systems-components/zeeltronic-programmable-ignition-controller/

[m in sc]

two totally different ignitions, so no.  id focus on tuning at this point instead of throwing parts at it just yet. (aside from brass)

[Organicjedi]

Thanks, everyone. Yes it sounds like I have some dialing in to do. First 2 stroke street bike for me so didn't know what to expect.

Anyone know if the Zeeltronic Programmable CDI (link below) will work with the dyna S pickups?

Im ordering new sprockets today and a 520 chain so Im sure I will be much more happy since the stock gearing is tall.

New pipes are not really in the budget at the moment. Im really debating putting stock back on the pipes are VERY loud. Or course the trade off may be worth it.

https://www.economycycle.com/product-category/yamaha-rd250350400r5ds6ds7-parts/electrical-ignitions-lighting/ignition/cdi-ignition-systems-components/zeeltronic-programmable-ignition-controller/

What size sprockets did you go with? My '77 is modified SIMILAR to yours (still several differences). I dropped one on the front and went up one in the rear. It pulls great down low and breaking 100 is still way too easy to do. 

For the loud pipes, check your packing material. My spec II's didn't have much in there from the get go. JSpooner ID'd this for me and helped me repack mine. A repack might help the sound. I will say, finding stock pipes for a Daytona will probably be an expensive endeavor.

[racerclam]

WEll the absolute best thing to provide more linear power and better bottom end grunt and reduce or eliminate light switch power is to have me fabricate venturi dividers at 1/4 1/2 and 3/4 throttle positions. It becomes like opening 4 small carbs in series . Function? Air on the air filter side is grabbed and directed under the slide the passes to a equal height divider and air is kept from expanding into the larger area past the slide , air speed stays up all the way to the reeds . This also allows the use of bigger carbs with out the down fall of BLAH! A UFOs with this is great also, I usr UFOs in every carb I do and I do alot . Also I dont know how your port work was done , but I have concepts that improve performance throughout . Important is that all transfers and boost port open at exactly the same time as well as the boost port . Boost port angle from factory is also wrong and needs to be altered. A the exaust port shape needs changed too. And also I add a case port , it connects the intake directly to the crankcase which helps every where too. On and on I can go. Call me if you are interested . 702-858-9177

Rich

[racerclam]

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