Effect of using wrong spark plug?

[TomC]

Hi, I needed some new spark plugs which I got a friend too buy, but when I got them I was stupid enough not to check they were the right ones before opening and installing one, not knowing about them I took the attitude of if they fit then they are right. Anyway looking in the derbi senda manual I have it says i need NGK B8ES, the ones I have are NGK BP7ES. Does this matter? if so what will the effects be?
Sorry if it is a stupid question, I am inexperienced in bikes.

[Scotsman37]

If the manual says thats the ones to fit and then that is the ones to fit because the wrongs ones may overheat, etc. The manufacturer has designed the combustion chamber and so has designated that the recommended spark plug is the one to fit because it was incorporated into the design when they originally engineered that bike.

[cagiva gezzer]

This explains all

You've just moved one notch down the heat range so it will run hotter. No biggy, just might be slightly more prone to overheating and slightly less prone to fouling.
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"because one stroke isnt enough and four strokes waste two"

[TomC]

would it be wise to run with these plugs? bearing in mind i am in the process of rebulding the topend and replacing the entire piston and dont want to do any damage.
Thankyou for the replies.

[Scotsman37]

If you like the idea of seized engine and then having to do a rebuild then go ahead and use them. My friend just advise me that a bike dealer once installed the wrong spark plugs in his old RD250 and ended up having to get the above done. The spark plugs blew apart !

You've been warned !

[cagiva gezzer]

It will be fine to use during the run in period as the bike will be at lower revs and not getting up to temp, but i would change back to the recomended plug once its run in. I normally change the plug at the end of the run in period as they get rather dirty.

If you're running a modded engine, then i would use a BR9.

I ran my derbi on a BR9 all the time as its an easier plug to get hold of.
____________________
"because one stroke isnt enough and four strokes waste two"

[TomC]

ok cheers, wouldnt happen to know if halfords would sell them or not? Anyone know if halfords are open on a sunday? cant find out on their site.

[Scotsman37]

Yes, Halfords is open on Sundays and they've got motorcycle section and that's where you'll find the bike spark plugs and you'll also find next/nearby it a bike model spark plug guide to find the correct spark plug for your bike.

[TomC]

cheers chief