K3B hight end miss / Inection timing

[trx400r6]

Bolens G174 (tx1510F) Mitsubishi K3B

engine would never make full rpms when I first bought it, could only make about 2100prm, the high speed setting bolt was in too far, adjusted it 2 turns out to start and can now make about 2600rpm however anything over about 2100-2200 it really starts to miss bad... this is not under load however as I don't have any of my attachments here at the house. I tried running it up to full rpm while in high gear and holding the brake a little to put some load on it but still had a pretty bad miss...

tractor starts great and doesn't miss a beat under 2000rpm. my first thought would be injection timing but usually that would mean hard starting as well... anyone else have any ideas or had a problem like this?

also if it is injector timing where are the actual shims? on the bottom side of the pump by the tappet that rides on the cam shaft? parts diagram in my re-print manual doesn't really have a very good picture kinda fuzzy....

thanks for anyone with any advice!

KC

 

[Ilikeurtractor]

My K3B does this too on my TX2160 at around the same rpm as yours (2400-2600). I also have a Launtop diesel (Yanmar L100 air-cooled China clone) that missed at high rpm. Both of these are elusive to me but I'm thinking the K3B is due to the governor cutting fuel at the higher rpms (to limit engine overspeeding) but I never dug into it enough to be sure. The only thing I can theorize is the Launtop lacks the needed air intake quantity at higher rpm. The exhaust temps would go through the roof and it would start blowing white smoke, almost like combustion was taking place (incompletely) in the exhaust rather than in the cylinder. I used to live at a higher elevation and after I moved to a lower one (i.e. higher air pressure) it seems to be not as pronounced but still there at the very high end of its rated speed. Maybe now the governor is causing it (?) I actually need to play with it more. It hasn't been that much of a problem as I don't usually run at maximum rpms a lot. I would like to know what it causing it so keep us posted if you find any other symptoms or the solution.I haven't noticed this problem on my KE75 and it will run up to 3000 rpm without missing. I haven't noticed this on my Satoh either which has a K3A but I need to check next time I'm on it.

The shims are under the pump. Generally you don't need to mess with timing on these engines unless you're experiencing cam wear which I haven't noticed as being a problem with anyone.

 

[trx400r6]

Thanks ILUT I don't really wanna mess with the timing... I gotta do some more research before I pull anything apart cause from the parts diagram the governor assembly kinda scares me lol but I would like to take a look at the weight/springs and make sure everything is ok on that front... might try adjusting the control rack slightly give it a touch more fuel as the governor goes up...

my symptoms may change with a good load on it as well, im headed up north to the hunting land today to bring my brush chopper back to change blades and gear lube and such so will hook it up and test out with a load on it in the next few days and report back...

KC

 

[Ilikeurtractor]

Yeah, it's best to stay away from the governor and pump unless you're having a shop do the work but then get ready to dig deep into your wallet. The actual problem may be more in the pump itself rather than the governor flyweights and associated linkage. It seems like the pumps on the K3 engines are a fair amount more complicated than those on the KE series engines as a side note.