Sorry that's happened, but still a lovely machine, well worth doing. I am very surprised there's no brass overflow tubes in the carbs. That's crazy. Keep up the good work.
That Haynes manual is mainly about the T250 Derek. I wonder why they stopped using the overflows on the GTs? Mine is a GT250M (1975) and it does have drain plugs below the cylinders. Shame I didn't use them! Mine has filled a silencer or two completely with petrol on more than one occasion. - always my fault for leaving it on 'Prime'. Hope you get yours going again soon, they are lovely bikes.
Same happened to mine Derek. Mine blew the seals out the side! There are two possible reasons that I know of, either the diaphragm in the petcock is not working or you left the petcock in the 'Prime' position. If the petcock is in 'Run' or 'Reserve' petrol will only flow when the engine is turned over and the diaphragm opens. Hence no need for an 'Off' position. Left in 'Prime', the petrol eventually gets past the float valve (or valves if you're really unlucky) and pours straight into the engine - either above or below the piston depending on where it was at the time.
I have a Haynes manual and it shows a photo of the carbs with the overflow tubes fitted. Its a tube that goes up inside the float bowl and exits at the bottom in the middle of the bowl. On mine they are blocked off. There are a few differences, the manual also shows sump drain plugs and one way valves in the oil feed lines that mine dosnt have. I have checked the float valves and the vacuum tap today and they both seem ok so I cant trust either of them. I have taken the spring out of the fuel tap so the fuel is on all the time and will fit another fuel tap underneath the vacuum tap that can be turned off. re the hole in your tank, mine was the same also it was very thin right underneath the petrol filler as you look inside. I welded a large curved plate underneath with a mig welder. If its just a pin hole I would either spot weld it with the mig or if the metal is thin I would braze it with low temp silver brazing rods using map gas. But be warned its EXTREAMLY dangerous either method and unless you know what you are doing DONT.
I have had a think and I agree that the petcock must be at fault because it was definitely switched to the run position which is off when the engine is stopped. First the fuel has got from the tank to the engine when it was in the "off position " so either the fuel has passed the tap and gone down into the carbs and the float valves have failed as well or the diaphragm in the tap has a hole in it and fuel has gone down the vacuum pipe into the engine. Spoke to the local motorcycle mechanic ( old school ) and he said that bikes from the USA don't have overflow tubes as the regulations in the US don't allow fuel to be vented on to the ground. So before This engine is started again that daft fuel tap will be gone and some kind of carb overflow fitted, I might also fit some drain off plugs in the sump. This must have been a known problem that's why that vacuum tap has been fitted so its not possible to leave the petrol turned on when the engine is stopped ( in theory) So beware owners of imported gt250s and sleep tight.
I don't think any of them had overflow tubes Derek, mine's a UK bike, that's how they were. I guess they expected 17 year olds to remember to sort the petcock out before riding. My engine is with Dirt and Road bikes in Shipley. Dave Cowell knows his stuff, and rebuilds cranks properly, he has some videos on here of mine (recent) and another one about 2 years ago. Same problem. Thanks for the great videos Derek. As a fellow old school restorer, I think you're doing an amazing job. By the way, I have a really good tank that I took back to the bare metal. I revealed a tiny hole at the back bottom part§, where the welds are. Any ideas as to what I should do?
I have seen Dave Cowell videos on here. Your tank you could use a chemical liner. I have used them with success but once one went bad and liner didn't take, It ended up like a big plastic bag in the tank I had to buy some chemicals to remove it. I later welded it.
You can't turn the fuel off is 1 problem.. I've made the mistake leaving the tap on prime and it dieseld on me cause the crank was full of fuel. I pulled the plugs out and cranked the fuel out and replaced the plugs... finally I got it going again without it going spastic on me
Sorry that's happened, but still a lovely machine, well worth doing. I am very surprised there's no brass overflow tubes in the carbs. That's crazy. Keep up the good work.
I had same thing happened to me in the day. On a GT 380. It was a failure on the centre oil pipe .
That Haynes manual is mainly about the T250 Derek. I wonder why they stopped using the overflows on the GTs? Mine is a GT250M (1975) and it does have drain plugs below the cylinders. Shame I didn't use them! Mine has filled a silencer or two completely with petrol on more than one occasion. - always my fault for leaving it on 'Prime'.
Hope you get yours going again soon, they are lovely bikes.
Same happened to mine Derek. Mine blew the seals out the side! There are two possible reasons that I know of, either the diaphragm in the petcock is not working or you left the petcock in the 'Prime' position. If the petcock is in 'Run' or 'Reserve' petrol will only flow when the engine is turned over and the diaphragm opens. Hence no need for an 'Off' position. Left in 'Prime', the petrol eventually gets past the float valve (or valves if you're really unlucky) and pours straight into the engine - either above or below the piston depending on where it was at the time.
I have a Haynes manual and it shows a photo of the carbs with the overflow tubes fitted.
Its a tube that goes up inside the float bowl and exits at the bottom in the middle of the bowl. On mine they are blocked off. There are a few differences, the manual also shows sump drain plugs and one way valves in the oil feed lines that mine dosnt have.
I have checked the float valves and the vacuum tap today and they both seem ok so I cant trust either of them. I have taken the spring out of the fuel tap so the fuel is on all the time and will fit another fuel tap underneath the vacuum tap that can be turned off.
re the hole in your tank, mine was the same also it was very thin right underneath the petrol filler as you look inside. I welded a large curved plate underneath with a mig welder. If its just a pin hole I would either spot weld it with the mig or if the metal is thin I would braze it with low temp silver brazing rods using map gas. But be warned its EXTREAMLY dangerous either method and unless you know what you are doing DONT.
I have had a think and I agree that the petcock must be at fault because it was definitely switched to the run position which is off when the engine is stopped.
First the fuel has got from the tank to the engine when it was in the "off position " so either the fuel has passed the tap and gone down into the carbs and the float valves have failed as well or the diaphragm in the tap has a hole in it and fuel has gone down the vacuum pipe into the engine. Spoke to the local motorcycle mechanic ( old school ) and he said that bikes from the USA don't have overflow tubes as the regulations in the US don't allow fuel to be vented on to the ground. So before This engine is started again that daft fuel tap will be gone and some kind of carb overflow fitted, I might also fit some drain off plugs in the sump. This must have been a known problem that's why that vacuum tap has been fitted so its not possible to leave the petrol turned on when the engine is stopped ( in theory) So beware owners of imported gt250s and sleep tight.
Mate had a WR250F flow fuel into the engine through an open valve... By the time he went to ride it the engine was full to locking point :-/
them crowns are cooked
I don't think any of them had overflow tubes Derek, mine's a UK bike, that's how they were. I guess they expected 17 year olds to remember to sort the petcock out before riding. My engine is with Dirt and Road bikes in Shipley. Dave Cowell knows his stuff, and rebuilds cranks properly, he has some videos on here of mine (recent) and another one about 2 years ago. Same problem. Thanks for the great videos Derek. As a fellow old school restorer, I think you're doing an amazing job. By the way, I have a really good tank that I took back to the bare metal. I revealed a tiny hole at the back bottom part§, where the welds are. Any ideas as to what I should do?
I have seen Dave Cowell videos on here.
Your tank you could use a chemical liner. I have used them with success but once one went bad and liner didn't take, It ended up like a big plastic bag in the tank I had to buy some chemicals to remove it. I later welded it.
You can't turn the fuel off is 1 problem.. I've made the mistake leaving the tap on prime and it dieseld on me cause the crank was full of fuel. I pulled the plugs out and cranked the fuel out and replaced the plugs... finally I got it going again without it going spastic on me
Its been sold now I was sick of it.
cool video but can't you pick up your feet when you walk? lol
I have had english lessons in school.... useless