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Thank you all for the kind comments

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mine vibrates at around 5k rpm but not nearly as bad as you say yours is. does it have good rubber bushings on your handlebar risers?

Ill definitely check this.

make sure  all the motor mount bolts are tight, particularly the front mounts

Yes, they are tight. Thank you for the suggestion.

Handlebar bushings, foot peg bushings. Most of these are blown out and no good. Worth a look. Tighten motor mount bolts for sure! Also, a set of bar end weights really helps. The heavier the better!

I have to check the handlebar bushings. I just installed footpeg bushings from yambits.

Exhaust pipe rattling?

Theres no rattle as such, I checked it today. But the exhaust gasket (the connection between the cylinder barrel and the pipe) is missing and there seems to be a sealant instead. Next thing on my todo list is to order the diamond shaped gasket.

Also the bolt support (near the footpeg) for the DG is missing a grommet when I checked the parts diagram, but its snug. Ordering the grommet too.

Handlebar bushings, foot peg bushings. Most of these are blown out and no good. Worth a look. Tighten motor mount bolts for sure! Also, a set of bar end weights really helps. The heavier the better!

Will try this for sure

the only time i ever had oen vibrate really badly, was 1 time i had one that once carb slide pin back out and the RH carb hung wide open, and it actually twisted the crank as i couldnt get it to shut down. not saying thats what happened here, but after everything else is exhausted, nut and bolt, timing, carb synch, etc, that might be worth a look.

The pin is good. I know what you mean. Happened to a friend of mine, but in his case, he just switched it off. Youre running the HPI right? Im running it too, so the keys are basically useless on mine, since I havent figured out how to ground the HPI onto the key system, I use the engine kill switch, which is also in reverse. On is Off and Off is On.

I have a 75' RD350B US Spec. The front end vibrates so much after 5K RPM; that my hands and elbows hurt. Low end of the RPM band is fine. I bought it this way 3 years back but was too excited to care then  This is what I did:

1. It was missing a rear engine mounting bolt. I bought an OEM piece off a part-out bike hoping it would fix the issue, but it didnt affect the vibration even a tiny bit.
2. It was also missing the rubber dampers in the cylinder head/fin. I bought the whole kit off yambits, installed it and again, it didnt help 1 bit.

It came with a DG pipe, 210 main jets, and uni filter, rest is stock. How can I get rid of this vibration?

This one.

What is the advantage of using non resistor type boot? Does it give better power?

I read on treatlands website that the HPI unit has to be used with resistor type spark plugs or boot, either one, else, it will burn the CDI unit. Im not really good with electronics. Please advise.

https://www.treatland.tv/HPI-CDI-mini-rotor-ignition-system-yamaha-RD350-p/hpi-yamaha-rd350-mini-rotor.htm

I used to be getting 13.8V DC on my RR @2000rpm after ungrounding the coil lead, but not anymore. It's only giving out 5V @ 2000rpm now. I'm trying a bunch of stuff to find what's going wrong.

Others have successfully done it. Ill troubleshoot this summer and if there's still no luck, I'll be running the whole system AC.

Installation was fairly easy although the included installation manual was very helpful. Take out the existing generator (use the following video):
https://www.youtube.com/watch?v=RYW1hOxFfOQ

Once you remove the rotor and stator, you will find a small dovel pin which needs to removed with a plier, only then will the HPI stator install correctly aligned. I have attached the image (ITEM NO 14 in the image). Also remove the woodruff key in the crank as the HPI is a taper fit onto the crank.

The markings made by HPI on the rotor were correct, so i just needed to use a dial gauge to set the timing. Mine is set at 3mm BTDC. There are 2 separate set of markings on the HPI stator, so use the 2nd set of markings, when you consider that the crank/rotor motion is counter clockwise.

The stator connection goes to the CDI, then to the coils and then to the spark plugs. I use the original kill switch, but the polarities are reversed,  meaning ON IS OFF and OFF IS ON.  Iv seen some posts saying that using a relay will fix this but im ok, i can live with that, I call it theft deterrence (especially since im bad with electronics) 

Generally, i found that the bike was much easier to start with the HPI. Not sure about power difference since my bike is not a 100%. Leaks here and there that needs to be fixed first.

 :taz:Running into issues again. I am only getting DC 5V-2 Amp at 2000 rpm. Voltage goes up to 13.5V only after 5000 rpm. My battery cant keep up with it. Currently running a lead from the ungrounded end of the coil along as 1 input to the RR and the HPI supplied light-out as the other IN for the RR. These 2 go into the input of the R/R.

I even bought a trailtech R/R  (model 7004-RR150) which is a full wave 150 watt RR with a relay, suspecting that my existing ebay RR might not be working. Voltage is dropping as RPM increasing! 

Any  help is greatly appreciated

Got mine in 2020. I guess it must be a newer model as the stator has a scale like timing mark in it. Each 5th mark equals 1 mm, was easy to play around to check power difference at different ignition settings. Tried between 1.8mm and 3.5mm BTDC, got the best power at 3mm BTDC. Finally used a dial gauge to recheck since I was following the scale on the stator and it was almost exact.

Does the coil end need to be grounded? (the thick metal square that looks like a battery terminal)

Can i use a non-resistor type spark plug with a HPI CDI unit?
Some says it will burn the CDI.
Some say it will only cause electrical interference with the CDI box and can be fixed by moving the CDI box away from the plugs.

I feel atleast 20% reduction in power with the NGK BR8HS resistor type spark plug.

Hi, what is the spring size for the DG pipes for a 1975 RD350B?

There are quite a few options on Economycycle. Pic attached.

Installed the Rectifier+Regulator today.

I took a line from the black wire, close to the plastic connector near the CDI unit, to feed the R/R. I didn't run a seperate snake line from the stator.

Removed the m4 allen as advised and taped it up; to un-ground.

Got a steady output of 13.6V / 5A at idle. Finally found the engine kill switch wire and connected it to the cdi (picture attached, the red+black wire). Thank you M in SC, quocle603 and my brother for the valuable tips.

Im trying to get the motorcycle running with battery. I bought the ATV 4 wire R/R from ebay.

I now have only 1 lead to the R/R, which is the HPI yellow "light out". How can i unground the coil, so I have 2 leads to the R/R. Also, how does this ungrounding affect the ignition voltage?

Thanks, how about the R/R?

I will check today and revert the voltage at different rpms.

In the meanwhile, I read on treatlands that i need a resistor type sparkplug or a resistor boot. Should i buy this ->

https://www.ebay.com/itm/NGK-Spark-Plug-Resistor-Cover-Cap-Boot-NEW-LB05F-Motorcycle-Elbow-5k-Ohm/202777608821?fits=Model%3ARD350&epid=26017010018&hash=item2f367cc275:g:z4AAAOSw7I5TsZP4:sc:FedExHomeDelivery!14305!US!-1

Also, on another page, i saw that the member bought a rectifier+regulator, will this help me to hook up the hpi unit to the battery to power everything  ->
HPI is out of stock on their R/R, and thats almost a 150 bucks as well. This one on ebay is 10 bucks.


https://www.ebay.com/itm/4-Wire-Full-Wave-Silver-Motorcycle-Regulator-Rectifier-12V-DC-Bike-Quad-Scooter/292689887133?pageci=9699c8a5-f3b7-4164-8330-44b7047f5d53&epid=828261382