BSA Owners' Club Workshop Discussions

The BSA Workshop => Bantam - pre 1973 => Topic started by: K Walton on 02 Jun, 2025, 16:49

Title: D7 Running Problems
Post by: K Walton on 02 Jun, 2025, 16:49
Have an issue with my D7 when it is on the stand and the engine running , at high revs, and you close the throttle. the engine takes a long time to slow down ( the carb slide is not sticking ) and there is a lot of banging, which almost sounds mechanical, but is not I get the same symptoms when riding it, It was suggested to me that  I should try enriching the mixture by raising the needle 1 notch The carb by the way is pretty new, probably only done 500 miles. This had no effect. The bike is fitted with Electrex World electronic ignition.

Any one have any ideas.

 Thanks in anticipation
Title: Re: D7 Running Problems
Post by: Catz on 02 Jun, 2025, 17:27
I've had that before but on my FJ1200. It sounds like the mixture screw is set to running too weak and i'd go with your suggestion of enriching the mixture.
Just re-read your post and at the end you say "this had no effect". What had no effect? Enriching the mixture or the new carb?
Title: Re: D7 Running Problems
Post by: K Walton on 02 Jun, 2025, 19:12
Enriching the mixture
Title: Re: D7 Running Problems
Post by: rhyatt on 02 Jun, 2025, 19:28
2 strokes often jangle and sound /feel jangly on the overun.
You have 2 scenarios , when in gear the reducing roads peed will pull the engine down.
When just running on its own , the momentum or mass of the flywheels will take a while to slow down
Title: Re: D7 Running Problems
Post by: rhyatt on 02 Jun, 2025, 20:31
Quote from: rhyatt on 02 Jun, 2025, 19:28 2 strokes often jangle and sound /feel jangly on the overun.
You have 2 scenarios , when in gear the reducing roads peed will pull the engine down.
When just running on its own , the momentum or mass of the flywheels will take a while to slow down

On the overun , but also when running light or no load.
The minute you hit an incline , it will clean up nicely
Title: Re: D7 Running Problems
Post by: cdsdorset on 21 Sep, 2025, 23:05
The late Paul Harker cured this phenomenon. He found a suzuki head with the same stud spacing and centre plug. He remachined the squish to suit.
He said it scared him to death the 1st time he throttled off at a junction and the engine went quiet  ;D