Hello all, I have an issue with my '73 F9 Bighorn 350 that I recently rescued.

As soon as I put her in 1st from a standstill, she leaps forward and stalls out. This is with the clutch lever still squeezed...the only way I can get moving is to put her in 1st while rolling at 3-4mph and then let the clutch lever go.

Also shifts kind of hard through all 5 gears. It feels like the clutch is not disengaging from the flywheel fully when I pull the lever? (if that's even how it works...I've yet to learn the inner workings).

The bike has "sat-up" for nearly 10 years - could that have something to do with it? I'm pretty decent DIY mechanic with cars, but have no experience working on bikes. I would greatly appreciate any advice as to where to start troubleshooting.

Thanks!

 

Warped clutch plates, too-thick oil, or clutch cable in need of adjustment.

The previous-generation Ninja 250 was notorious for the 1st gear lurch, they somehow cured it in 2008. Heavy oil exacerbated the problem. I can't count how many times I killed my '94 in the driveway simply by kicking it into 1st gear. Completely new clutch components, synthetic oil and nearly all the freeplay adjusted out only helped a little.

Try adjusting most of the freeplay out of the cable (leaving a few mm between the handle and base when you release the clutch). Fresh 10W-40 oil is the next method, followed by all new clutch plates (I'd replace the fibers as well).

 

Thanks 94ninja250. I was hoping a cable adjustment might fix it, i'll give it shot. To my knowledge the oil hasn't been changed since the 70's so I guess that needs to be done regardless of whether or not the cable adjustment works! The bike only has 3500 original miles, so I doubt it's the clutch itself.

it's a 2-stroke btw, so i'm running premix with the oil injection system disconnected. I've read that the injection system sends oil directly to the crank pin as well as near the rotary valve where the fuel comes in - I guess I need to find a way to keep the crank wet either by rehooking the injector system or just adding oil to the case manually - I don't trust the system for the oil/fuel mix tho, i've heard horror stories about the oil pump crapping out and ruining the engine from lack of oil...

anyone familiar with 2-strokes know if it's possible to have the injector system feed oil only to the crank pin, so i can still run premix, but not ruin the crank?

it's an "Injectolube" system similar to the Superlubes found on the F5 250's I think....

 

The first thing you want to do when you revive an old motor is change that oil. Make sure your starting off fresh, who knows what 40 year old oil will do...

 

The oil injectors from what I remember were prone to clogging. Lack of oil.

 

Here's what I found late last night: oil was a little low, but remarkably clean. Adjusted the clutch cable which tightened up the lever quite a bit, but still no dice. With the engine off I can shift into first, pull the clutch lever in, and she still won't roll freely. I can hear what sounds like the clutch moving inside the LH cover when I squeeze the clutch lever though. Time to remove the cover and see what I find...