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Two bikes and neither run...

Everything about swapping a motor on your Virago.
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Two bikes and neither run...

PostAuthor: Freediver17 » Tue Oct 10, 2017 9:38 pm

Hi, I am new to this forum and need advise. Currently I own a 1981 xv750 and a 1982 xv920. After finding that the xv750 had a seized cam, the running xv920 engine was swapped to the 750 frame. The 920 engine had an oil leak during the swap and was thought to be remedied during process with a new oil cover and gasket. Once running the swapped engine ran for 23 miles until she was blown from lack of oil...

I currently have a swapped 920/750 that doesn't run, a seized 750 engine in the corner,and a 920 frame with a slew of patrs in the shed. My goal is to build two completely different bikes out of my pile of parts. I need to know what my best plan of action should be for a complete first build on a budget.

My questions are; should I buy another engine to swap into my 82xv750 frame? If so, what second generation engines would be the easiest swap for the most performance? Are the cams in each engine the same, so I could possibly repair the 750 cam with the 920 cams parts, being that they are the same generation? What are the differences between 750 and 920 engines in regards to internal workings, besides piston size?

Freediver17
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Bike year & model: 1981 xv750 virago and 1982 xv920 virago
Sex: Male

Re: Two bikes and neither run...

PostAuthor: ers_bikes » Tue Oct 10, 2017 10:31 pm

According to Partzilla.com the cams should swap.
I would try to rebuild the 750 1st gen.
Not sure if the 2nd Gen would bolt on, and it would need a harness/electronics swap. (You could try one of the listed subject chains to verify yes or no)



This Yamaha 4X7-12171-01-00 CAMSHAFT 1 is used on these models and components:

1981 VIRAGO 750 - XV750H CAMSHAFT
1981 XV920RH CAMSHAFT
1982 VIRAGO 750 - XV750J CAMSHAFT
1982 XV920RJ CAMSHAFT
1982 XV920RJ CAMSHAFT
1983 MIDNIGHT VIRAGO 750 - XV750MK CAMSHAFT
1983 VIRAGO 750 - XV750K CAMSHAFT

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Bike year & model: Various assorted Viragos and others 1981 750 to 2003
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Re: Two bikes and neither run...

PostAuthor: nanno » Wed Oct 11, 2017 6:20 am

All engines up to the XV1100 will bolt into your 750 frame, with regards to cams, all the cams (even the most contemporary VStar 1100 cams) will bolt in. Be aware, that most likely you will also have to get a set of new rockers for your cylinder head.

If you want to bump up compression on your 920/1000/1100, you best install a set of 750 or 700 heads. These do have smaller ports, limiting peak HP to around 6000rpm, but USABLE torque kicks in a bit over 2000rpm. Basically shifting the powerband down roughly 1000rpm.

If you plan to run a post 1984 XV750/1000/1100, you will either have to swap over the loom from those donors OR swap rotor, stator and ignition pickups. Be aware, that if you plan to run a late 750 or 1100 with the bulgy alternator cover and the old alternator, you have to either have a roughly 30mm spacer made or find one out of a very late XV1000. On the other hand, a late 750 or 1100 rotor won't fit under the old cover.

Personally I'd go for an XV1100 engine, 700 or 750 heads, but with later hardpad rockers and cams and a set of nice VM38 or TM38 carbs and a good exhaust. If you really need more horsepower, buy a Ducati or a Buell.

Cheers,
Greg
P.S.: These are all conversions that I have DONE myself, so that's not hear-say.
http://viragotechforum.com/viewtopic.php?f=12&t=43227 - Nanno's accumulated findings (and blatant show-off) - infos on my TR1's, my performance and reliability mods and a bit of show-casing of the stainless steel exhausts I build

http://greasygreg.blogspot.co.at (My blog - Greasygreg.blogspot.co.at)
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Bike year & model: 1984 XT500
1985 SR500
1981 Yamaha TR1
1982 Yamaha TR1 Turbo
1973 DS7 (RD250) Racebike
1977 XS 750 Sidecar
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