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SP1000 carb choice

RKS_DK

RKS_DK

Tuned and Synch'ed
Joined
Jun 19, 2016
Messages
32
Location
Denmark, Hadsund
So, I bought a 82 SP1000 completely stock, but needs some rebuilding.

Among other things I want to replace the carbs, it came with the stock VHB30's

I plan on some aftermarket exhausts, but no other "tuning"

What would the best choice be and why?

Been looking at PHBH 30 and PHF30, big price difference?

Would it make sense to fit 36mm instead? and what would the consequence be?
 
I'd stick with 30s. Choice of which ones is yours. As you increase carb size, optimum RPM for good air fuel mixing goes higher. I think you will find that the 30s will have the optimum RPM at the speed you would ride. Also the stock square slides work well so I'm not sure why you would want to change if they are in good working order.
 
I agree with John Z. the throttle response is better with the 30s for this motor. I switched to 30 round slides on my T-3 to match my SP-NT (red/wht). I swear I got better response, but I think that may be my mind justifying my extra curricular tinkering. I have an extra set of the 30 square slides, maybe 2 sets, if you're look'n.
My SP relatively stock, but do have Mafac(?) fork cartridges, UNI sock air filter (1 long to fit between both carbs), SPII handle bars with bar backs (much more comfortable), G-5 mufflers, saddle bag rack and clam shells. Custom Triumph side stand, made by an old mechanic in the '70s, Dyna ignition, Valeo starter and Odyssey battery and SS brake lines.

Make sure you rebuild the calipers with seals aluminum pucks, that will probably save the rotors from warping.
also the rear drive splines are vulnerable to rust if they where not greased before storage.

good luck, post a pic.
 
Ditto...why do you want to replace the carbs? If the carbs (and the rest of the engine) are in good condition and set up properly there is not much to be gained in adding new 30mm carbs.

However adding some 36mm carbs with some head work to match will liven up the bike nicely if that's of interest to you.
 
Was a barn find basically, it Was sluggish and "heavy" carb leaking All over. and slides Worn

So plan to get New carbs and dyna Ignition. and get it All adjusted

Head work seems vers pricy here so Will just get it running best as possible
 
Doesn't really matter as they all work well. I think the PHF type is what was used on later bikes and may be easiest to mount as the late model bikes used a different manifolds which will be needed to mount them.
 
Incase I asked a workshop to port the top end- what would I tell them? I assume they need to machine some of the intake duct, but how much? maybe get some bigger valves?

Otherwise, thanx alot for the info :)
 
You are limited by valve size. Porting may help, but maybe not enough to give you the performance you want from larger carbs. The cost vs benefit ratio may not warrant the expense of working on the heads to possibly get the benefit of larger carbs. See the spreadsheet here for calculating carb size https://www.guzzitech.com/forums/resources/categories/misc.24/
 
If you are not changing to bigger carbs there is no need to do anything to the head other than clean the carbon from the ports and combustion chamber and have the valves and seats machined so they are sealing properly. The valve guides my also need re-sleeving if there is significant wear. Any good automotive machinist or cylinder head shop should be able to do this for you.

If you want to fit larger carbs, fit some le mans inlet manifolds and have the inlets ports opened up to match the manifolds. Some tidying up around the valve guide is also beneficial. Very little work is required but best to find someone who knows Guzzis. The valve sizes will be fine with bigger carbs. The small valve heads can be made to flow very well, the shape of the backs of the valves are very efficient. With the carbs set up properly this mod transforms the low/mid range of the engine. At the top end you are still pushing a barn door fairing so can't expect to much!
 
Depends on the market and vintage maybe Amboman...my 650 NTX doesn't have the accelerators.I'm in Europe.
 
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