Q: I’ve just fitted a top box (maker’s name withheld because my brother sells them) to my 2005 Aprilia Caponord. I’ve wanted to fit one for a while now because my backpack gets wet in the rain and I live just outside Durban where it tends to rain a lot. So it seemed like a good idea to fit a waterproof carrying device.
The fitment of the accompanying brackets in the kit was relatively easy, if not a little fiddly, but I came right in the end. So then it was time to go and out test the new ‘box on the open road.
As soon as I get to 140km/h the bike has now developed a constant weave, which is a bit unnerving, and I didn’t feel like going any faster to see if it disappeared at higher speeds.
So, is this trait common when one fits a top box and more importantly is there anything I can do, or try, to cure the problem?
A: If the top box you’ve bought isn’t primarily designed to fit this particular bike problems, like this, can occur. Also, there’s probably a label, or sticker of some kind, on the ‘box, advising on speeds after fitting it. So it might pay to find that.
Also, if a pillion sits on the back it sometimes stops this ‘weave’ because it smoothes out the airflow after it passes over your body, try that? Also, move your body position backwards and forwards whilst riding to see if that improves things. But as a rule you’re going to have to keep your speeds down, live with it, or take it off when not really needed.
Q: I see you’re getting a lot of questions relating to older Japanese motorbikes, so I thought I’d throw another one at you.
I have a Suzuki GS550 from the late seventies, just because it’s all I can afford. It still has points and condensers, which are always giving me loads of problems. I’m forever cleaning them and settings gaps, etc, which is irritating to say the least.
I’ve just priced a new set from Suzuki (two sets of points and two condensers) and they come to nearly R1,000, WTF! And within a few years they’ll need to be replaced again, and the entire mechanism seems to be worn out anyway.
So what other options do I have? I’m thinking of replacing all of it for an electronic system, and would you know who to get in touch with, and will it work OK with the stock ‘points’ coils?
A: I would certainly throw away all that old stuff and replace with a modern conversion from Dynatek for example. You’ll get a much more accurate spark and better all-round performance, and it will work fine with your stock ignition coils.
Go to www.dynojet.co.za and order your parts from there, they are the official South African importer for the full range of quality electronic parts, like these, from the USA. Then your points problems will be over with your ol’ GS.
Q: Morning men. I’m about to rebuild an old Kawasaki GPZ1100 from 1982, the one before the Unitrack rear end arrived. I’ve taken off the head and barrels to check out the state of the piston, rings and valves. I’ll have the valve seats cut again for maximum compression and the piston and rings are within Kawasaki’s tolerances, so I’ll just hone the barrel.
But I’m thinking of raising the motor’s compression ratio by skimming the head and or barrel, which one would you recommend and more importantly, how much would you take off and what compression hike can I expect? Would this affect performance, and if so, by how much? According to the manual the standard compression ratio is 9.5:1.
Thanks for your time and now waiting for your reply.
A: First off all do not attempt to skim the barrel; it will cause all sorts of problems regarding the piston height and therefore clearance issues. So you can certainly skim the head and it will indeed raise the compression ratio to a more modern figure.
We’ve done a calculation and recommend taking off 0.5mm from the cylinder head, make sure a proper engineer does this though, because if the head is machined incorrectly you might as well throw it into the bin, you have been warned!
This will raise the compression ration from 9.5:1 to close to 10.8:1, which is quite an increase. Set the ignition timing to stock and use 95-octane fuel and you’ll certainly feel a difference in performance, possibly a 10% increase, or even more.
Hope that clarifies the process for you.
Q: Hello to you all. Please can you help me with a recent issue regarding my 1984 Suzuki GSX750?
I’ve owned this bike for the best part of my life and it has over 80,000km on the clock, I say over because the speedo broke about a year ago, but that is not why I’m writing.
My wife and myself have been on many trips with no problems, and the bike has always been serviced at the correct intervals. But recently when the bike is in top gear, and after a few kilometers, the bike just dies. I then have to shut off and rev the engine until it begins to run smoothly again.
I’ve fitted a new air filter because the old one is, well, too old, and drained the carbs by undoing the screw under the float bowl. I also fitted new spark plugs, but the problem still remains.
So please can you tell me what to look for next because we still want to keep the bike because we still enjoy it and don’t really have the money to buy one of these new and too complicated expensive machines?
Korbus (and wife).
A: It might be time to have someone, who’s a qualified mechanic, to take off those carbs and give them a thorough overhaul and service. You can still get some genuine parts from Suzuki, if you need them.
However, bikes of this age can generate problems with the vacuum fuel tap. If the diaphragm inside the tap is worn or leaking it will certainly starve the bike of fuel in a manner you’ve mentioned. There are vacuum tap rebuild kits for sale on the Internet, so check that out by taking the tap off, dismantle, clean and inspect it, and also the internal screen filter as well for blockage.
Another thing to easily check is the breather for the petrol tank, if blocked or restricted this will also cause this issue. So take of the fuel cap, strip it down, blow through all the parts with an airline, and see if that helps. Push the bike backwards and forwards to swill the fuel around and make sure you can hear air escaping from the filler cap to make sure it’s functioning correctly.
Go through these recommendations and I’m sure your loved machine will be fine again and give you many more hours in the saddle, with your wife of course.