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CB750 / CB750K0 Carburettor Problems
« on: April 04, 2014, 08:26:43 PM »
Hi all,
My other half has a 1970 CB750K0 which has been causing problems for a while now, it looks stunning but has had consistent carburation problems which we can't solve.
The bike is reluctant to pick up at RPMs less than 3500 - when the throttle is opened it initially dies and then suddenly picks up. There is a considerable amount of hesitation when riding at around 30-40mph. It is also a nightmare when trying to pull away, for example at a junction, he has to rev it and ride the clutch to stop it from dying half way through pulling out. However, the tickover is very sweet, and at higher RPMs (for example, cruising at 50mph plus) it picks up fine.
The carbs have been balanced several times now, just after they have been balanced it runs beautifully, but once it's been left for ten minutes it's all over the place again. It has been checked for air leaks (by spraying fluid onto the engine to see if it temporarily improves) and there are none. Plugs all look perfect.
The bike has been restored to a very questionable standard by a 'professional' company, and it has taken 9 months to even get it running and on the road. However we are now really stuck with the carbs. They have had new carb kits fitted, but we are beginning to think that the carb bodies themselves are worn, and the bike will never run properly with these carbs on it.
Has anyone else experienced anything like this? My other half is now looking to source another set of carbs for it, if anyone has any they would be prepared to part with..?
Cheers,
Steph..
My other half has a 1970 CB750K0 which has been causing problems for a while now, it looks stunning but has had consistent carburation problems which we can't solve.
The bike is reluctant to pick up at RPMs less than 3500 - when the throttle is opened it initially dies and then suddenly picks up. There is a considerable amount of hesitation when riding at around 30-40mph. It is also a nightmare when trying to pull away, for example at a junction, he has to rev it and ride the clutch to stop it from dying half way through pulling out. However, the tickover is very sweet, and at higher RPMs (for example, cruising at 50mph plus) it picks up fine.
The carbs have been balanced several times now, just after they have been balanced it runs beautifully, but once it's been left for ten minutes it's all over the place again. It has been checked for air leaks (by spraying fluid onto the engine to see if it temporarily improves) and there are none. Plugs all look perfect.
The bike has been restored to a very questionable standard by a 'professional' company, and it has taken 9 months to even get it running and on the road. However we are now really stuck with the carbs. They have had new carb kits fitted, but we are beginning to think that the carb bodies themselves are worn, and the bike will never run properly with these carbs on it.
Has anyone else experienced anything like this? My other half is now looking to source another set of carbs for it, if anyone has any they would be prepared to part with..?
Cheers,
Steph..
There's no warning at all, no coughing, just a sudden complete cut out. The bike also sometimes takes a while to start again afterwards so may be fuel related? Electrics all still work at the time of the cutout.
)
Only a few more bits to go now: crash bars to fit, having one of the side panels repainted, and trying to get a gear shift lever in good condition.
It'd be great to make contact with anyone else in the area, as I only have Triumph boys to ride with at the moment!