Carb backfire, M10, Twin 40's

[Reck]

Looking at the twin-40 equipped M10, what is the most likely cause of carb backfire and how would I go about diagnosing it? i.e. expected behaviours at different rev ranges for the differing causes?

I'd basically like to rule out any issues with the valves which would involve taking the head off.

[nas80]

usually its the engine timing or the carb setup that causes a backfire.

Its a whole different ball game doing these side drafts properly and you have to keep adjusting them now and then to keep em in check.

more often then not they make an engine drink fuel like no tomorrow.

[e21-Mark]

Have you had the engine running with a single carb?

Where are the 40's from? Do you know they're jetted correctly and in good condition?

If you like tinkering 40's are simple enough to keep in tune but as Nas said, they need fettling and maintaining. You need to make sure the linkage is all correct and that both carbs open in sync too.

[GerritBuggenhout]

Can it harm your egine if you set it to backfire on purpose?

[Reck]

I don't know. I don't like the idea of flames in my engine bay though!

[drjim]

Have you bought it mate, or just thinking. Sorry I couldn't come round to listen to your engine over the weekend, A&E very busy!

With regards to setting up a pair of weber sidedrafts, I would suggest you drive tohttp://www.ricwood.com and get him to fettle.

Jim

[Reck]

Have you bought it mate, or just thinking. Sorry I couldn't come round to listen to your engine over the weekend, A&E very busy!

With regards to setting up a pair of weber sidedrafts, I would suggest you drive tohttp://www.ricwood.com and get him to fettle.

Jim

Still thinking! I'm in no rush to be honest. I might be going down this weekend or early next week. I might even flog the dual carbs if they give me too much of a headache as I still have the Weber in good nick on my old M10.

Yeah no worries about coming rounf, I can imagine Crumpsall on a Saturday morning probably looks like a war zone!!

[drjim]

Sunday night is far worse.

You also have working EFI - much better than sidedrafts for a daily driver.

Did the RAC man come and tow it to the garage??

[Reck]

Why's that? People arguing over their Sunday dinner?

Not had the RAC down yet. If we're serious about the plan for my old wheels, then it might be worth saving my free tow for getting it to your workshop!