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Retrofitting '85-'87 Beluga Parts onto your '81-'84 Beluga

 
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DandyDan
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Joined: 17 Oct 2007
Posts: 1076
Location: Victoria, BC

PostPosted: Sat Dec 15, 2007 9:51 pm    Post subject: Retrofitting '85-'87 Beluga Parts onto your '81-'84 Beluga Reply with quote

Typically an early model ('81-'84) Beluga will top out at 35-40mph whereas a late model Beluga ('85-'87) will be able to reach 45 or even 50mph. The reason for this is that for the 1985 Model year Yamaha significantly improved/redesigned the engine in a whole bunch of ways. Accordingly, if you want to improve the performance of your early model Beluga it's best to take advantage of these improved parts before you venture out and start finding aftermarket parts for other scooters. Here is a list of the key parts that you need to obtain in order to upgrade your early model Beluga:

- Cylinder (Radically different ports and new intake manifold location)
- Head (Perhaps the old design is compatible but this head is noticeably different).
- Spark Plug (Protrudes into the cylinder less)
- Piston (had cutouts on top to accommodate new intake location)
- Rings (not necessary but always a good idea)
- Exhaust (new exhaust port means the old exhaust won't work).
- Carb (this one is better and the other one is too small to fit)
- Airbox (fits with the new carb)
- Reed Cage (completely different part)
- Cap for old reed cage mounting spot

Those are the main parts that you need. There are also a few small parts (gaskets, hoses etc) that I haven't mentioned. You're likely best off to just buy a complete late model engine from eBay and then toss that in and sell your engine. If you're savvy you could do this for perhaps a profit since early model engines are more popular and thus presumable easier to sell.

Another issue that you face if you just retrofit the above mentioned parts (like I did) instead of swapping the engine is that the crankcase does not entirely match with the new cylinder ports. As a result, some of the area of the new ports is partially blocked off. I am going to try running mine as is but if I suspect I am losing signficant performance then I'll try to fix this with my Dremel which doesn't appear to hard. You essential have to dremel/grind the crankcase opening a little bigger in a few spots. Here are the '85 (back) and '83 (front) cylinder gaskets. As you can see circled in red are the areas of the '85 ports that are obscured by the smaller case opening.


Another thing to consider when you are planning/installing this is if you are going to use the late model exhaust and carb or use aftermarket ones. In my opinion, the exhaust is probably pretty good but the carb is still quite a bit undersized so you may want to toss on an aftermarket one as described here:
http://cv80.phpbbweb.com/viewtopic.php?t=16
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DandyDan
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Joined: 17 Oct 2007
Posts: 1076
Location: Victoria, BC

PostPosted: Thu May 22, 2008 6:23 am    Post subject: Reply with quote

To update this thread, I changed my mind and dremel the ports in the late model cylinder to match my early model case. It wasn't too hard...it took me maybe 2 hours with the Dremel.

Using either of the base gaskets seemed like a poor idea because nether really lined up that well. Accordingly, I ditched the base gasket and uses some high temp engine sealant instead. This has been working well for about 1000kms (600 miles) now and it has the side benefit of increasing your compression ratio a hair. On the downside, there are a few areas of the sealing surfecae (as previously mentioned) that do not have a lot of contact. This doesn't change when you match the ports but by using sealant instead of a gasket you might have leakage issues. I had a minor leak when I first installed the cylinder so I re-did it and it seems to be sealing well now.

On hind sight, I should have really just paid $175 for that used late model engine on eBay. I paid nearly that for the parts I needed and I don't have the upgraded drivetrain parts that were changed with the engine revisions....plus I had to do a lot more work and it may not be as reliable.
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TwistTheGrip
Junior Wrench


Joined: 20 Apr 2010
Posts: 7
Location: North America

PostPosted: Thu May 06, 2010 5:40 pm    Post subject: CV 50 VS CV 80 & 86 Yam Jog Reply with quote

Did the late model 50s get better also like the 80's??
Is the CV 50 and 80 the same except for cylinder and carb??

How different is the CV50 from a 86 Yam Jog as I would like to use the CV case if it the same as the CV 50 has a much bigger brake (front and rear) (rims much fatter as well) than the 86 Jog???

Thanks,
Twist
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