Left Cylinder missing when Hot

[KANDY]

Hi All,
My friend's 1973 RD350 has an issue, it runs fine for some time and shows missing on Right Cylinder while on Traffic and eventually dies. He Kept idling high to tackle this issue, but the issue persists. Could you please advise on this, or gouide me to the post which discuss this in the Past. This Bike is Running 30 Pilot, 120 Main and Stock Needle and Needle Jet. 1 1/4 on Air Screw. Stock air box with Yambits Air Filter. Engine is Ported as per Previous Owner(dont know How far). This Bike had Dave F Mod done before with DG Pipes, he converted all Back to original set up to solve this issue.

[SoCal250]

Has he tried swapping coils, L & R?

[KANDY]

I guess - No
Let him try and will get back

[m in sc]

yup. coil

[350GUY]

Hi All,
My friend's 1973 RD350 has an issue, it runs fine for some time and shows missing on Right Cylinder while on Traffic and eventually dies. He Kept idling high to tackle this issue, but the issue persists. Could you please advise on this, or gouide me to the post which discuss this in the Past. This Bike is Running 30 Pilot, 120 Main and Stock Needle and Needle Jet. 1 1/4 on Air Screw. Stock air box with Yambits Air Filter. Engine is Ported as per Previous Owner(dont know How far). This Bike had Dave F Mod done before with DG Pipes, he converted all Back to original set up to solve this issue.

Kandy: You need to up-jet. Main jet size #130 is the std. size for the RD350.

[SoCal250]

Hi All,
My friend's 1973 RD350 has an issue, it runs fine for some time and shows missing on Right Cylinder while on Traffic and eventually dies. He Kept idling high to tackle this issue, but the issue persists. Could you please advise on this, or gouide me to the post which discuss this in the Past. This Bike is Running 30 Pilot, 120 Main and Stock Needle and Needle Jet. 1 1/4 on Air Screw. Stock air box with Yambits Air Filter. Engine is Ported as per Previous Owner(dont know How far). This Bike had Dave F Mod done before with DG Pipes, he converted all Back to original set up to solve this issue.

Kandy: You need to up-jet. Main jet size #130 is the std. size for the RD350.

Actually the stock main jet is #140 for the early models with the unbaffled air filter 278-14451-00-00 (anything pre-RD350B, engine # ~308121).
When Yamaha changed to the "new style" baffled air filter 360-144551-90-00 in mid-1975 model year the jetting was changed accordingly, decreased to #105.

I believe the Yambits filter is the unbaffled version, so yes he would likely need to upjet from current. I don't think that's going to address his issue though.

[m in sc]

correct. yambits filter is unbaffled and should be a 140

[350GUY]

Besides jetting, could also be fuel starvation........

[quocle603]

Ive had bad coils before and it does suck when it kicks in and out at times. I would also double check timing, I was chasing a jetting issue that turned out to be a timing issue all along

[KANDY]

It was bad coil. Both coils measured Primery = 4.2 and Secondary = 8.8 so never suspected. I changed with similar reading coils and the issue is no more. May order Suzuki SV650 coils in the future as per M in SC in other post. Changed the Main to 130 now, I think the bike need 140.

Note : Now the Bike is at 130 Main, 30 Pilot - Airscrew -Just below 1 rotation, Leanest clip position on the Jet needle - Running moderately good, there is hesitation around 4000 RPM, Planning to go 32.5 on Pilot and 140 on Main then see where the clip postion should be, what you guys think. Had 300 plus km done today without any issues, but could be better - so thought above set up.

[Twill864]

Economy cycle sells emgo direct replacements for like $35

[m in sc]

it should pull a 140 main.

yeah, ive had coils bench test ok but take a shit when in use. it happens. glad you found it.

[quocle603]

Coils can be gremlins at times. Good for a bit or in different scenario and just crap out. Then be fine again. Always good to replace old vintage ones