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Yamaha dragstar xvs400 to 650 Conversion


pike2112
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Hi All,

Just joined this forum so please be gentle with me!

I want to convert my sons 1999 xvs400 dragstar Classic to a 650. I understand that the two engines are the same except that the 400 is a sleeved down version of the 650?

Can i simply fit a set of 650 pistons and barrels to the 400 bottom end and fit the original 400 head to the new barrells?

I believe the carbs are the same for both models Mikuni BDS28 x 2. i'm guessing I will have to re jet (Main and Pilot)?

Also, will the 400 exhuasts fit to the new 650 parts or will I have to invest in a 650 system?

finally, if the top end conversion isn't an option, will a 650 engine just bolt in as a replacement with obviously a carb set up to suit new engine size?

Any advice would be greatly received

cheers

pike

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The 400 is an import only version and not all that common, either...

You'd probably get enough money selling it to buy a good nick 650 and still have change for custom add-ons, extra gear and a trip round the country!!

Unless you're a mechanical hobbyist and fancy doing the 400 mods for fun?

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The 400 is an import only version and not all that common, either...

You'd probably get enough money selling it to buy a good nick 650 and still have change for custom add-ons, extra gear and a trip round the country!!

Unless you're a mechanical hobbyist and fancy doing the 400 mods for fun?

so much for going easy on me eh ;)

Yes I am an enthusiast with many years of mc and amatuer mechanics running my own rides, a ducati monster and hack cb250rsa (if you're lucky enough to remember one) and yes my son and i do travel around the country lots but unfortunately he's restricted to a 33BHP bike. The reason i want to do this is because the rest of the bike is in excellent condition with plenty of history and has been running without missing a beat.

So back to my original questions...is this possible or are the 650/400 top end engine parts not interchangeable?

thank you and look forward to some advice

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so much for going easy on me eh ;)

Yes I am an enthusiast with many years of mc and amatuer mechanics running my own rides, a ducati monster and hack cb250rsa (if you're lucky enough to remember one) and yes my son and i do travel around the country lots but unfortunately he's restricted to a 33BHP bike. The reason i want to do this is because the rest of the bike is in excellent condition with plenty of history and has been running without missing a beat.

So back to my original questions...is this possible or are the 650/400 top end engine parts not interchangeable?

thank you and look forward to some advice

have been doing some further research into this and don't belive the 650 top end conversion will work or indeed be worthwhile.

I think the main problem is the bore stroke calculation. the current 400 is a 68 x 55mm Bore/stroke. adding a 650 piston will not (I believe) change the stroke eg 650 bore 81mm with same stroke 55mm at best will give me a cubic capacity of around 550cc. I guess will equate to a few extra horsepower?

So I'll try to tune with perhaps a k&N filter and re jet.

I guess fitting a 650 motor complete is an optionbut they are very few and far between...don't go wrong much!

Cheers all

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so much for going easy on me eh ;)

That was going easy.... for me, anyway :lol:

The other option was for me to say "Haven't got a clue", so I opted for the more useful reply.

have been doing some further research into this and don't belive the 650 top end conversion will work or indeed be worthwhile.

As I thought.

I don't know what would be involved in a swapover, but I'd guess it's more time, money and trouble than it's worth, unless you specifically wanted to do it as a fun project.

I guess fitting a 650 motor complete is an optionbut they are very few and far between...don't go wrong much!

Not if they're looked after, no...

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