Our youngest took over my 2015 MT-07 back in 2017, after I totaled his CB400SF. It has done 22k miles (or 35k km, really) since new, and today I changed the spark plugs in it for the first time. I could have saved me the trouble, because the original spark plugs showed virtually zero signs of wear, with the gap still identical to the new plugs, and the center electrode still flat with sharp edges.
So, what does it take to change the spark plugs on the Yamaha 700? You start by removing the seat, meaning removing two bolts under the seat pad. You literally bend the rear flaps of the seat away, with force, to gain access to the bolts. By design! Then you need to remove the side panels that cover the tank plus bits under the seat, one panel for each side.
First, you need to find one of these on each side, used to connect the rear of the panels to the panels under the pillion pad
Very cramped access, children's hands an advantage. Once these are removed, you need to remove two bolts on each side, plus two bolts on the rear, plus one bolt holding a pad on top of the "tank", and another 4 bolts under the pad, and then pull the panel out of its three rubber mounts while at the same time trying to separate it from the center piece living under the pad without breaking anything. Now, with both side panels removed, you can remove another pair of pins like those shown above, another pair of bolts, remove the center piece, and then another pair of bolts and their bushings that hold the surround that live around the tank lid, plus it also forms the front of the "tank".
Done? Not nearly. Now you remove four bolts holding the rear of the fuel tank, and lift the rear up before supporting it on a piece of 2x4 that everybody have laying around. Right? Now you unplug one pin from a sensor, one multi-pin plug from the fuel pump, and release the safety clip securing that the fuel hose cannot be pulled off the fuel pump. Only this was already sitting in the released position, so someone have been in there before and forgotten to secure it. Finally, you can remove the front bolt securing the tank to the hinge mount and lift off the tank.
All these are tedious and time consuming, but not really difficult. The real struggle is about to begin now. Because you need to unclip both coils, that are also the spark plug caps, without having access. Well, with pains and cuts you will manage to unclip the right one, but the left? Well, the manual does not call for it, but draining the coolant system and the coolant hose to the top end MAY have give enough clearance, but I eventually managed to unclip it with a couple of screwdrivers instead.
Getting the coils to let go of the spark plugs take a huge amount of effort, which is very difficult when you cannot grab them. Lots of fiddling and levering with big screwdrivers and wooden stick eventually moved the free. However, while the manual call for them to be moved up, this is not easy since "up" is blocked by wires and brake hoses and brackets on the right, and the main wiring harness on the left. Oh, I forgot to mention you also need to remove an air pump above the coils, one that again does not give access to normal tool with an 8 mm socket needed to remove its retaining nut.
The brake hoses would not be there on models without ABS, but this bike has ABS. So I removed a retaining bolt that gave a minute, but precarious, 2/5 inch of sideways movement. Still, it took 20 minutes just to wriggle and force the coil past all the bits in its way and out into the free. And that was the easy one. The left one took nearly two - 2! - hours to get out, including removal and replacement of the spark plug and refitting the coil. Pure hate! I am very proud of myself that I managed to stay calm and focused, because violence would not have helped.
The coil cannot be moved enough out of the way, you (I, at least) cannot reach the coil or access tools to screw the spark plug out of in, and the tools cannot get a straight line from above to be fitted into the very narrow hole - the spark plugs are just 14mm, and require a thin walled socket that much reach deep into the engine. Plus you have nearly an inch of thread length to struggle with!
All in, from start to finish, with panels in place and bike finished, I reckon I spent around 5 hours. I could have saved at least an hour by draining the cooling system, even taking into consideration removing and refitting the parts of the coolant system. Also, I work slowly, and in unfamiliar territory. Still, compare the five minutes of slow and deliberate time it takes to change the spark plugs on an XVS650 or any Virago, and it is easy to see that this bike is made stupid.
If you want to look at more torture, check out videos of valve adjustments on bikes like the CRF300 Rally or 390 Adventure. Or the MT-07 - we just ignored going in there since there is nothing to suggest it is in need of a valve adjustment. But I shudder when reading through the process.
After the MT-07 debacle, I went inside and ordered a single carb conversion kit from Mikuni for my Virago. I will never complain about carbs again. Ever. Carbs are bliss! Simple maintenance is even better. The kind you find on a KZ440 or W650 or RD350 or...
