New here, so apologies if I’m not wholly familiar with the posting rules.
I’m hoping to acquire a full service manual - so far I’ve downloaded a 134 page pdf manual which is helpful but insufficient detail and its for a “V7 Classic” which is probably not exactly the same. My main question is about the stated gear ratios.
The manual says “Main transmission, gear ratio 16/21 = 1:1.3125” which is arithmetically correct but what does “Main transmission” mean?
The ratios are arithmetically correct also for gears 1 through 4 but 5th gear says 22/25 = 0.9 which is not! Also, final drive with cardan shaft, ratio 8/33 = 1:1.4825 but 33/8 = 4.125. Is this a typo or something I don’t understand?
And maybe the Racer ratios are different anyway?
Most grateful for any clarification, and whether a proper service manual can be bought
Thanks, Adrian
The 2012 V7 racer workshop manual is available on the Guzzitek website. Hopefully that will answer your questions.
https://www.guzzitek.org/gb/accueil_gb.htm
Thanks Don-Spada, the Guzzitek website is where I already found the 169 page V7 Service Station Manual which is helpful but clearly not a complete workshop manual I was hoping for - I should have said “workshop manual” in my original post. The numbers I mentioned were taken from that service manual - so I’m still struggling!
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Guzziology would be the other option, that has a section on gearing. It is available as an e-book download £7.50 or to purchase as a paperback copy £37.49 from Amazon.
https://www.amazon.co.uk/Guzziology-Version-9-Dave-Richardson-ebook/dp/B07L39NDC6
Useful looking book, although the feedback suggests it covers a whole range of moto guzzis so this kind of detail is probably not included for a specific bike - unless someone knows different? I found another link which says the 5th gear ratio is 18/20 = 0.9 which is arithmetically correct and a general explanation of primary drive in a bike gearbox so I’m nearly there. May buy that book anyway as it looks interesting!
The book gives quite detailed information about gear ratios. Unfortunately my copy is old and so doesn’t cover the newer V7 models. This is an extract of the page on small block gearing to give you an idea of the information available.
I’m sold! The ratios and tooth counts for the primary and all five gears of your second table are the same as I have for the V7, only the final drive is different. I confess, I’m looking at using the engine from a salvage bike for a Pembleton style ‘old timer’ replica using a a 2CV or Alfa boxer (33/Sud/145) gearbox so the final drive ratio is not important but I’ll need to strike a compromise with gearing and wheel size since the idle speed of these V twins is necessarily quite high. Many thanks for your quick and informative responses!
Ah, if you are building a Pembleton, that reminds me of a guy in Northampton that was doing the same. He put me onto a very good website that had lots of info about Delorto carbs. It also has tons of info about Pembleton builds. I assume you are aware of it.
https://www.thepembleton.org.uk/index.shtml
He was using a 650 Nevada engine mounted to a 2CV gearbox with adapter plates that he had made.
You are a mine of information! That’s an excellent site and the downloadable manuals show exactly the kind of detail I really need. Sadly, my more recent engine is fuel injected with an electronic ECU. I’d like to revert to carbs but my understanding of the IVA test is that they judge engine emissions on the age of the engine so I will almost certainly need to stick with EFI to pass. I plan to build a 4 wheeler - 3 is just too dangerous, especcially with a V7 engine.
The 2CV boxes are becoming as rare as hens’ teeth with prices to match and they are not as robust as the alfa romeo transaxles. I’ll certainly have to get an adapter plate made, but I wonder what others do about adapting the clutch plate to fit the gearbox splined shaft - probably a question already answered on the site.
Don’t laugh, but ChatGPT thinks, when asked, that I could use a wasted spark ignition coil to fire both spark plugs at once! Given that one cylinder approaches TDC as the other is in the middle of its induction stroke this might be a bit pyrotechnic - we are safe from being replaced by AI for a while longer I think.
Good luck with your build. I think you have exhausted my knowledge of Pembleton builds, but I do see the website has a forum so you should get plenty of help on there.
It is certainly possible to run a V7 on carbs, someone did it a while ago when putting a new engine into an older bike. Not sure what ignition option he used? As you say, emissions may be an issue.
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Thanks for all your help. I’ve tried to register with the Pembleton site but I’m stumped by the question which is intended to stop robots. The question is “what is the name of the famous public school at the end of Pembleton” which, given that Pembleton is not actually a place, has me completely lost 
That’s a great one to confuse you. The answer is Eton 
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Of course it is! How stupid am I? No need to answer that
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What a great question lol I wonder how long it will be before bots can answer this
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ChatGPT was most apologetic that it couldn’t find a place called Pembleton
