Hey all! So I picked up a 1973 bonneville 750 and hard tail frame for $1000 yesterday. Motor was out and just a rolling frame. He says engine was not stuck and he was going to rebuild it but has no time or money to finish. He said he rode and ran fine before he took the motor out. The motor has been sitting for 8 months. I get it home take the plugs out and try and kick it over by hand and it wont budge. The bike is in neutral. So I take the top end off to the cylinders(I was going to rebuild the top end anyway)and pistons look good...not seized etc. I can move the pistons side to side and wd-40 drains past the pistons into the crank case. Still wouldn't budge. Took the primary off to see if maybe the clutch was stuck...no problems there. I took the kick start out and everything looks good there too. So Im thinking maybe the crank may have issues? Or maybe a transmission issue that is not allowing the motor to kick over? The motor is on the bench so I cant really put the bike in gear and try to rock to free up the transmission. So before I totally break this thing down...is there anything I am not thinking of? This my second triumph and is bit of a learning curve for me...all help is greatly appreciated! Thanks y'all!
1973 bonneville 750 engine issue
- Thread starter mwm1977
- Start date
just because you can rock the pistons doesn't mean the rings aren't stuck continue with some wd40 while heating up the barrels
heat up the barrels slowly and let the heat soak, try again rotating while hot
put a wrench directly on the crank end but don't overly force it.... is there any evidence water got innit ? like in the timing chest?
heat up the barrels slowly and let the heat soak, try again rotating while hot
put a wrench directly on the crank end but don't overly force it.... is there any evidence water got innit ? like in the timing chest?
Well I took the cylinders off and one of the connecting rods looks to have been starved for oil and is fused to the crank...so the motor is going to get completely rebuilt. On a positive note, I get to learn/rebuild the entire motor and I have one of the best vintage British bike mechanic/racer 45 minutes from my house to help guide me through the process! Thanks for the help XB!
pidjones
Over 1,000 Posts
I had a TR6C (basically a single carb bonny) 650 that seized a rod bearing due to the crank oil ports being plugged solid with sludge (don't think the PO ever changed oil) the crank, however was shiny smooth and all it needed was a set of bearings, which the mechanic showing me how to split the cases (for free) sold me for $8. All I had was $20, so he left me with gas money to trailer it to my next duty station 600 miles away. The tranny in-and-out of the case was the tricky part, and he did that for me while I watched closely. That was early 70s.mwm1977 said:
Make sure you rod out that crank and all oil passages! Should flow kerosene or other fluid cleanly. I hope you are lucky like I was.
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