Thanks for a very nice view of an old monobloc. It's been probably forty years since I worked on my last one, but I've got a feeling I'll be looking into the amals on my 78 Bonneville, it's not as smooth as it ought to be, and it's new to me. That ultrasonic machine does a great job, I'm thinking I need one.
Thanks very much Mike. It really does make all the little parts shine like Jewelry. I'll schedule a time with you Monday or Tuesday to pick up the carb at work. I'm available any time. Very nice video Mike, as usual.
Great video Mike. Am going to service a 385 tomorrow. Had a cold run out on the Shadow earlier on to pick up a service kit, so looked for a video to give me an idea of what I’ll be up against, and this popped up!
😉 thanks Graham! I hope all is well. We were hoping to have a club group ride tomorrow, but it's going to be snow and rain so unfortunately we have canceled. However we are still having the "garage crawl", so that should be a lot of fun seeing some really cool old Triumphs and Norton's. Best wishes, Mike
Thanks for the informative video plus the quality comments. I would like to clean my Bantam's 375 monobloc it's a disgrace to look at I can't imagine what the inside must look like. My problem though is a suitable solvent for the ultrasonic bath, where in the UK can I buy Simple Green? Regards Paul
Hi Paul, I'm sorry but I'm not sure where you can get Simple Green in the UK. You might try by starting with some general detergent. Possibly even something like fairy liquid (if they still sell it?). Best wishes, Mike
where can I get parts for this carb? I have a 67 T120R (USA version) with twin carbs. It's been sitting for years and I am missing the float needles plus those little brass spacers that keep the float away from the cover Could also use a gasket set.
Hi Scabaduu, if you screw the throttle stop screw in (turn clockwise), it will push the throttle slide up and increase the amount of the fuel to the carbs. Imagine it like you are opening the throttle. If you loosen the throttle stop screw out (turn anti-clockwise), it will lower the throttle slide up and decrease the amount of fuel to the carbs. Imagine this as taking your hand off the throttle and this should be used to help set the idle speed. I usually set it so that you can just see the tip of the throttle stop parallel with the top of the jet block and then do more fine adjustments when the bike is running. Good luck!
Thanks Dave. I think it helped. I seem to recall that he had a few other problems, but there were electrical and now his bike is running a lot better. Hope to see it again this year. Best wishes, Mike
The large main jet makes me wonder how the bike is running at full throttle. Does it have the typical symptoms of running too rich, i.e., not revving readily, sputtering, black smoke, wet spark plugs, etc.? My experience has been that some bikes now require bigger jets, compared to the past, due to lean running caused by crappy - I mean "modern" - fuel with alcohol in it. Another thing I've learned is that sometimes a weak ignition coil can cause running problems that mimic carburetor problems.
Hi Jim. Thanks for the note. I suspect that the changes made to it were to counteract the effects of the ethanol in the fuel but I'm starting to think what was done had the opposite effect of what was desired. The engine runs perfectly when cruising up to about 50 MPH on relatively flat roads. The throttle is barely open and it's quite happy. However, hills cause the problem. Opening the throttle to 50% or more causes severe starving. Full throttle and the engine quits firing at all. The last time I rode it, going up a hill on the way home it starting loosing power. As I gave it more throttle it abruptly stopped. I actually thought it seized. But I felt the head and it was at normal warm temperature. I cranked it and it started right up, running perfectly at idle and light throttle. So I rode it about 1.5 miles in 1st gear at 10-15 MPH to get home. The engine was perfectly happy. Normal temperature. That was in November. The last of good weather. Last week I drained the fuel tank thinking that maybe the filters were clogged causing the float bowl to dry out when going up hill because of the more open throttle. The tank and filters were perfectly clean and has full, strong flow. So i removed the carb thinking there was a problem there. Mike offered to put it through his cleaner and examine the internal parts. That is when he noticed the main jet was the size of the Bonneville jets instead of the TR6 jet size. I then mentioned to Mike that a work record I had with the bike stated that the needle was moved to the "1" position which is lean as possible. It also stated that the main jet was changed from a 330 to a 310. I believe this was a typo and the opposite was done because it has a 330 in it now. Running at idle and on flat roads it runs great. The plugs indicate very clean running. There is no smoke and the exhauset does not have that smell of unburned fuel. So when I put the carb back on I'll change the needle to position "3" which is the recommended setting. If it runs rich at "3" I'll change the main jet to 310 or lower as needed. I'm hoping this cures the problem. Again, thanks for your note, Jim. Thoughts?
It's strange that the engine stops firing completely at full throttle. I'd think that this would require a problem worse than just a slightly off-size main jet or a wrong needle position. The needle position usually affects mid-range running, but usually has little or no effect on full throttle running (I'm no expert regarding Amal carbs).. Maybe check to be sure that the float level isn't adjusted way low. Other than that, about all I can think of is some sort of defect/warpage that's allowing a lot of air to leak around the throttle slide at full throttle.
I would have agreed with you, Jim, until I did some google research last night. I found a tuning paper for the Amal Monoblock carbs somewhere and it was eye opening. It had illustrations of 5 different throttle positions and what parts of the carb are in play for each. The needle position is a huge influence at half throttle and up, just like I was experiencing. The positions on the needle are only about 2mm apart so it was hard for me to imagine changing from position #1 to #3 could make that much difference but the trouble shooting and tuning paper nailed it. Even a one-position change can have a major impact according to the paper. The carb has 3 fueling circuits that service different throttle positions. There is some crossover but not as much as you might think. The idle air adjustment, for example, is adjusted one last time once you get the rest sorted out so you get the best idle. I wish I had marked that page as I don't know if I could find it again. I also found conflicting information about the main jet. One paper had the 330 jet for single carb applications and much smaller main jets for dual carb applications. The monoblocks were used on many British bikes of that time so were tuned according to the needs of each. So, once I put the carb back on and test ride I'll probably have some follow-up tuning to do. I'm hoping that the needle setting change will cure the loss of power as described in the tuning paper and experienced on my bike when at half throttle and more. Thanks for your input, Jim.
Thanks for a very nice view of an old monobloc. It's been probably forty years since I worked on my last one, but I've got a feeling I'll be looking into the amals on my 78 Bonneville, it's not as smooth as it ought to be, and it's new to me. That ultrasonic machine does a great job, I'm thinking I need one.
Thanks very much Mike. It really does make all the little parts shine like Jewelry. I'll schedule a time with you Monday or Tuesday to pick up the carb at work. I'm available any time. Very nice video Mike, as usual.
Great video Mike. Am going to service a 385 tomorrow. Had a cold run out on the Shadow earlier on to pick up a service kit, so looked for a video to give me an idea of what I’ll be up against, and this popped up!
😉 thanks Graham! I hope all is well. We were hoping to have a club group ride tomorrow, but it's going to be snow and rain so unfortunately we have canceled. However we are still having the "garage crawl", so that should be a lot of fun seeing some really cool old Triumphs and Norton's. Best wishes, Mike
TR6C changed from 1 1/8" to 1 3/16" in '67 with a 330 main jet. Mid way through the production year swapped entirely to a concentric carb.
I had three animal carburetors nobody want to buy them so I throw them in the garbage can the recycler 2022
nice work,i have a q shall the air srew in or out to lower the rpm ,i have a 65 bonnie ,nice videos thanks
Hablas Español ? Very Good video , Tengo una Triumph TwentY One y justo hoy desarme el Carburador, Thanks You, Best Regards Miguel.
¡Hola Miguel! Gracias por tu nota. ¡Sí, hablo un poco de español con la ayuda de Mister Google! La Triumph 21 es una moto preciosa. Los mejores deseos
You haven’t mentioned the wear in the slide Most important. Happy days. John
A sticking throttle valve can be due to a not really flat flange. If you grind the flange ,the throttle will go on sticking. Not so nice...
Thanks for the informative video plus the quality comments.
I would like to clean my Bantam's 375 monobloc it's a disgrace to look at I can't imagine what the inside must look like.
My problem though is a suitable solvent for the ultrasonic bath, where in the UK can I buy Simple Green?
Regards Paul
Hi Paul, I'm sorry but I'm not sure where you can get Simple Green in the UK. You might try by starting with some general detergent. Possibly even something like fairy liquid (if they still sell it?). Best wishes, Mike
Normal running hardly use the mainjet or am I wrong? How bout fuel level, did you check this? And how...
Thanks a lot John for all your tips. Best wishes, Mike
where can I get parts for this carb? I have a 67 T120R (USA version) with twin carbs. It's been sitting for years and I am missing the float needles plus those little brass spacers that keep the float away from the cover Could also use a gasket set.
hello i have the same q for the trothle stop screw ,shall it in or out,to lower,the amount of fuel to carbs,thanks
Hi Scabaduu, if you screw the throttle stop screw in (turn clockwise), it will push the throttle slide up and increase the amount of the fuel to the carbs. Imagine it like you are opening the throttle. If you loosen the throttle stop screw out (turn anti-clockwise), it will lower the throttle slide up and decrease the amount of fuel to the carbs. Imagine this as taking your hand off the throttle and this should be used to help set the idle speed. I usually set it so that you can just see the tip of the throttle stop parallel with the top of the jet block and then do more fine adjustments when the bike is running. Good luck!
@@TheMightyGarage Hello yes ok I understand,is this similar on air srew,clockwise increase air,higer rpm?,thank you very much.
How'd it work when Scott put it back on the bike?
Thanks Dave. I think it helped. I seem to recall that he had a few other problems, but there were electrical and now his bike is running a lot better. Hope to see it again this year. Best wishes, Mike
The large main jet makes me wonder how the bike is running at full throttle. Does it have the typical symptoms of running too rich, i.e., not revving readily, sputtering, black smoke, wet spark plugs, etc.? My experience has been that some bikes now require bigger jets, compared to the past, due to lean running caused by crappy - I mean "modern" - fuel with alcohol in it. Another thing I've learned is that sometimes a weak ignition coil can cause running problems that mimic carburetor problems.
Thank you Jim for this great information. I will pass it along.. Cheers, Mike
Hi Jim. Thanks for the note. I suspect that the changes made to it were to counteract the effects of the ethanol in the fuel but I'm starting to think what was done had the opposite effect of what was desired. The engine runs perfectly when cruising up to about 50 MPH on relatively flat roads. The throttle is barely open and it's quite happy. However, hills cause the problem. Opening the throttle to 50% or more causes severe starving. Full throttle and the engine quits firing at all. The last time I rode it, going up a hill on the way home it starting loosing power. As I gave it more throttle it abruptly stopped. I actually thought it seized. But I felt the head and it was at normal warm temperature. I cranked it and it started right up, running perfectly at idle and light throttle. So I rode it about 1.5 miles in 1st gear at 10-15 MPH to get home. The engine was perfectly happy. Normal temperature. That was in November. The last of good weather.
Last week I drained the fuel tank thinking that maybe the filters were clogged causing the float bowl to dry out when going up hill because of the more open throttle. The tank and filters were perfectly clean and has full, strong flow. So i removed the carb thinking there was a problem there. Mike offered to put it through his cleaner and examine the internal parts. That is when he noticed the main jet was the size of the Bonneville jets instead of the TR6 jet size. I then mentioned to Mike that a work record I had with the bike stated that the needle was moved to the "1" position which is lean as possible. It also stated that the main jet was changed from a 330 to a 310. I believe this was a typo and the opposite was done because it has a 330 in it now. Running at idle and on flat roads it runs great. The plugs indicate very clean running. There is no smoke and the exhauset does not have that smell of unburned fuel. So when I put the carb back on I'll change the needle to position "3" which is the recommended setting. If it runs rich at "3" I'll change the main jet to 310 or lower as needed. I'm hoping this cures the problem. Again, thanks for your note, Jim. Thoughts?
It's strange that the engine stops firing completely at full throttle. I'd think that this would require a problem worse than just a slightly off-size main jet or a wrong needle position. The needle position usually affects mid-range running, but usually has little or no effect on full throttle running (I'm no expert regarding Amal carbs).. Maybe check to be sure that the float level isn't adjusted way low. Other than that, about all I can think of is some sort of defect/warpage that's allowing a lot of air to leak around the throttle slide at full throttle.
I would have agreed with you, Jim, until I did some google research last night. I found a tuning paper for the Amal Monoblock carbs somewhere and it was eye opening. It had illustrations of 5 different throttle positions and what parts of the carb are in play for each. The needle position is a huge influence at half throttle and up, just like I was experiencing. The positions on the needle are only about 2mm apart so it was hard for me to imagine changing from position #1 to #3 could make that much difference but the trouble shooting and tuning paper nailed it. Even a one-position change can have a major impact according to the paper. The carb has 3 fueling circuits that service different throttle positions. There is some crossover but not as much as you might think. The idle air adjustment, for example, is adjusted one last time once you get the rest sorted out so you get the best idle. I wish I had marked that page as I don't know if I could find it again.
I also found conflicting information about the main jet. One paper had the 330 jet for single carb applications and much smaller main jets for dual carb applications. The monoblocks were used on many British bikes of that time so were tuned according to the needs of each. So, once I put the carb back on and test ride I'll probably have some follow-up tuning to do. I'm hoping that the needle setting change will cure the loss of power as described in the tuning paper and experienced on my bike when at half throttle and more.
Thanks for your input, Jim.
Interesting. Like I said, I'm no expert on Amals. I hope the needle adjustment makes the bike run great!