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Needs to run like a proper 2 stroke.

 
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sc00ter
Master Wrench


Joined: 23 May 2010
Posts: 43
Location: norfolk, VA

PostPosted: Mon May 24, 2010 2:50 pm    Post subject: Needs to run like a proper 2 stroke. Reply with quote

Now that I got this 86 Riva 80 I 'm gonna tear into it and see what the little scoot has to reveal. I read most of the tuning page and luckily mine has the little "expansion chamber" exhaust and it flawless. I'm going to look into the reeds and see if I can cut some to fit (fiberglass reeds can be cut) and try to tighten up the throttle response. I'm going to pull the trans apart and check/maybe lighten up the rollers and look into the plastic sleeve behind the variator and see if its really a restrictor plate. Also going to increase the clutch springs to 2500/3000 RPM (3 shoe clutch as stock!) and go 10% up on the torque spring-if the one I have fits. It will touch 40 mph as it sits but I know it can do better. Not gonna go hog wild with it, just get it to run like a proper 2 stroke. It has 7000ish miles on it and the last 500 were all abuse. I had to rescue it, its just the coolest old school scoot ever! Will keep you posted on my results. Just gotta fix some small issues first with the rear brake and fix or replace the air filer box. Oh, and the prior owner "cleaned out" the carb and now the float bowl leaks gas BAD! Safety first.
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DandyDan
Site Admin


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

PostPosted: Tue May 25, 2010 6:51 am    Post subject: Reply with quote

Keep in mind the Riva 80 revs really low in it's stock setup. It's setup to rev really low, so even if you do modify the engine for more power you won't really be able to use it until you adjust the gearing. Going way lighter with the rollers (ie. 4-5g) will get it revving higher which will give you better acceleration and a higher top end because the stock the Riva 80 never revs high enough to make any power.
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sc00ter
Master Wrench


Joined: 23 May 2010
Posts: 43
Location: norfolk, VA

PostPosted: Wed May 26, 2010 5:36 am    Post subject: Reply with quote

Yes, the tall gearing is rather strange. Zumas are the opposite and everyone went with a over-range kit on them. Wonder what gear spacing the Riva reduction box uses? Since the Riva will be a loaner/learner I dont want it too fast off the line, just safe in traffic. Will post my results when I have time to try them. I have overtime for the next three months. Good for the walet, bad for the social life, horrible for scooter repair.
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sc00ter
Master Wrench


Joined: 23 May 2010
Posts: 43
Location: norfolk, VA

PostPosted: Fri May 28, 2010 2:46 pm    Post subject: Reply with quote

There is a mod that owners of the Honda Reflex 250cc like to do. They have the same issue as us with the weights being to heavy from stock so they take half the weights out. Instead of six you only have three, sounds strange, works great, plus you have replacements for later. Its called the K-mod. I thought of trying it with the Riva. Have to find my micro-tach first before I start messing with it so I can get the RPM's set right. I still have a ton of different 15x12 weights from my Zuma days. Also gonna see if a Malossi Multi-Var will fit, I have two extra's sitting around and the use of a full machine shop.
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DandyDan
Site Admin


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

PostPosted: Sun May 30, 2010 12:24 am    Post subject: Reply with quote

sc00ter wrote:
There is a mod that owners of the Honda Reflex 250cc like to do. They have the same issue as us with the weights being to heavy from stock so they take half the weights out. Instead of six you only have three, sounds strange, works great, plus you have replacements for later. Its called the K-mod. I thought of trying it with the Riva. Have to find my micro-tach first before I start messing with it so I can get the RPM's set right. I still have a ton of different 15x12 weights from my Zuma days. Also gonna see if a Malossi Multi-Var will fit, I have two extra's sitting around and the use of a full machine shop.


The downside with taking out half the weights is that you double the rate of wear on the remaining 3 weights since all the force is now going through half as many contact patches.

BTW, check out this video ('Night Top Speed Run') if you want to see how my '83 CV80 performed with the late model cylinder, late model reeds, technigas RS exhaust, 21mm oko slide carb and 4 or 5g rollers:
http://cv80riders.org/Videos.html

I learned later that my CV80 speedo actually read 5-7% low (GPS verified), so I was actually going about 55-56mph in that video and I could hit 60mph if I tucked.
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