Best Weight for RT-1 Flywheel?

[Tahitian_Red]

I ended up ordering a PVL for my RT-1 project.  Should I go with a slightly lighter weight than the stock flywheel (free-er revving and less bearing stress) or same/slightly heavier?

[vandy010]

mine weighs in at 1450 grams.
1650 grams is stock.
DT400 CDI set~up is 1800 grams.
i prefer the torque over the zing on these motors with 1450 grams as a middle of the road type of deal.
if that helps any

[OverTheHill]

RT's have big mains & will stand extra weight ok. Have a flywheel someone fitted a heavier brass ring onto & use it sometimes if i want a lazy feeling [but still powerful] motor. Takes the stress off the kick start gears too with the extra flywheel inertia. Something really you have to sort out for yourself & best if you're able to experience both options or have the ability to swap [light/heavy] depending on conditions. Digressing back to the "60's i had a B33 500 on methanol with 'cotton reel' flywheels, super high comp etc, was fast but ended up fighting it all over the track & went slower [lap times] than same motor with heavier [std B31 350 flywheels]. That's my two bobs worth anyway. Cheers.

[firko]

I've tried both the DT400 ignition and the PVL internal rotor ignition and I've found that I prefer the "lazy" heavy flywheel DT400's characteristics. Because the RT2MX engine has a pipey 250 style power band, I'll also use the heavier DT400 ignition to try and flatten out the torque curve a little.

Vandy, what did you do to achieve your 1450 gram flywheel? Did you machine down the DT400 flywheel or is there a lighter one available elsewhere in the Yamaha range?

[Tahitian_Red]

Firko,

Have ever weighed the PVL rotor?  I was planning to add about 500 grams to the weight of the rotor.

[David Lahey]

I used to enjoy riding George Mckenzie's modified RT3 (longer swingarm, LTR, lowered motor, RM front end) in the late 1970s. The motor was/is quite splendid. It had a chamber, mild porting mods and a bigger carby. The otherwise-standard RT3 flywheel had a steel band shrunk onto the OD. I don't think I would have liked riding it with the standard flywheel.

[TT5 Matt]

yz400d/e is lighter then the dt400 of the same era,then theres it250d/e as well which is a different part number to the yz400 so a few choices there to play with

[firko]

Firko,

Have ever weighed the PVL rotor?  I was planning to add about 500 grams to the weight of the rotor.   

No I haven't Jay.....I'm just about to leave the house for a big night out so I'll weigh it tomorrow and report in with my findings

[pancho]

 Like 'OverTheHill', I tried a set of lightened B31 flywheels fitted with a Manx conrod in my ultra hi comp B33 which proved totally useless. Instant wheel spin on tap.
 I would like to try a heavier flywheel on my old RT1 non reed valve.
 cheers pancho.

[vandy010]

Vandy, what did you do to achieve your 1450 gram flywheel? Did you machine down the DT400 flywheel or is there a lighter one available elsewhere in the Yamaha range?

1450gram jobbie is from a YZ490.(got the complete electrics set up cheap)
it took a bit of lathe work to get it to happen.
a good 1650gram set up is nice for sure. i machined the heavy DT400 flywheel down.
while the stock DT400 (1800gram) flywheel pulled like a tractor with gobs of torque, i just wanted a touch more zing so went lighter.

[firko]

I'll weigh it tomorrow and report in with my findings

I went out to the shed to weigh the PVL rotor this arvo but soon realised that both of my PVL's are already on engines. While I was sick earlier in the year I used up the boredom time by building two DT1 and three RT1 engines which used up my PVL stash. I've got a spare stator but alas no spare rotor to weigh.

I did however uncover an MX250 ignition that I didn't realise I had. Is there any difference between the MX250 and MX360 ignitions? Is there any improvements gained by swapping around CDI modules (black boxes) between different models? When I used the DT400 ignition on the DT1 from Hell I went from the stock DT black box to one from a YZ80 or 125 (too long ago to remember which) and definitely noticed more mid range, which was just what I wanted. I've got a decent stash of different older model Yammy CDI's and would like to do some mix'n'match experimentation on my test mule bike....Nathans old DT1. Any ideas?

[Tahitian_Red]

Got the PVL and the flywheel weight installed, but she is hard starting.  (2.3mm BTD)  Any ideas to help improve this?  This is not the cloth-wrapped model like I have on my CR480, but that is what the PVL catalog calls for.

 

[pancho]

 bump

[Tahitian_Red]

Bump start? 

[Iain Cameron]

Ive just got my hands on a nos SC500 full electrics including the CDI , when it gets here I think I'll try it out on a RT and see what its like . Iain