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Yamaha XS750


pedro32
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I have a 1979 Yamaha XS750 which has no spark. I have narrowed it down to blown transitor in the Electronic Ignition Module. It is about as big as a 10 cent piece and has FTD32 printed on it. I cannot read the rest because it has blown a hole where the part number is. Does anyone know the part number for this? Could it be something else that has blown it up? I was thinking voltage regulator maybe. Any help would be greatly appreciated.

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Hi pedro " contact Rex"s Speedshop. [ member] by PM, or his website, he"l do a refurb... :yeah:

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Thanks Mate

I have emailed Marcus from Rex"s Speedshop and he was quite helpful. I have ordered a second hand Ignition Module but I'm concerned that it will blow that one up too. Has anyone got any idea how the protection circuit works and how to test it? Below is a quote from an email from Marcus.

Its unlikely that part is available so it would mean I'd have to spend time looking for equivalents. I would need to know all the numbers, from the un failed item, to see if there is something available.

The other problem you might have is the protection circuit may have been damaged. When the transistor opens the circuit, the HT coil sends a 400 volt spike through the circuit. The transistor can't deal with this power surge, so there will be a circuit to protect it.

Any help would be greatly appreciated.

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  • 5 months later...

Thanx for your reply's. I found it was the indicator cancelling unit. Once I unplugged it everything behaved itself. Now I have a new question about the XS. Since I have owned it it has had K&N style pod air cleaners. I realise this isn't an ideal setup with this style carby but I don't have an air box to replace them. Does anyone know what size main jets would give me the best performance? I am having problems with it coughing and spluttering in the higher rev range whilst under load. If driven normally without giving it sh&@ it sounds and feels perfect. Thanks in advance

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Hi Pedro, I think (might be wrong!) that the K&N filters let more air in than the standard air box (lean) so you have to go up in size to compensate, best thing to do is see what you are already running and then go up in increments till you get it right, I don't think there is a specific number that will cure your problem you just have to do "a best guess" try your local bike mechanic for some ideas as to what might be the best jump in jet size.

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  • Moderator

there is a site that can give you the low down on the best way to tune the carbs

http://www.factorypro.com/tech_tuning_procedures/tuning_carbtune,CV,high_rpm_engines.html

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