Hi all,
Finally got around to booking my S10 into the Power Commander tuning shop in Ashburton New Zealand.
The bike has had a mid range stumble ever since I have owned it. I have spent countless hours testing coils and every other sensor the bike has trying to find the reason. I have had it since 60,000ks and it now has 87,000ks.
It has a full arrow exhaust, Uni air filters and a PC5 to adjust the fueling accordingly.
The guy that runs the shop is a Guru with PC.
He did some warm up runs towards 3/4 throttle and noted the air fuel ratio (AFR) was slightly rich but said it was acceptable and wouldn’t cause a stumble.
Then he did a full power run right out to 7,750rpm. It filled his dyno room with black smoke and when all that had cleared he shut it down and told me I had a turtle.
The bike made 78.5 HP and 45 ft/lb of torque!
The AFR went off the scale below 10.0. He took -20 off the 100% range and tried again. He managed to get 82 Hp out of it without the smoke this time.
After pulling up a previous S10 that ran 102HP completely stock on his screen we both came to the conclusion it either had no compression or the valve timing was out. Pulling 20% fuel out of a stock ECU map to get an acceptable AFR meant something was wrong.
Now I have ridden this bike for 18 months thinking the whole time it was fairly lazy but the 260kgs was the reason.I rode it home and pulled it apart.
Going straight to the camshaft timing I found the inlet cam was retarded by a tooth!
I’m guessing the bike hasn’t been right since it’s 40,000k valve adjustment... a test ride wouldn’t necessarily show it up unless the rider went WOT and thought it was lacking.
I did the 80,000k valve check and it was in tolerance so no adjustment necessary and no I didn’t check the valve timing
The tricky bit is the manual states to line up the exhaust cam and then count 4.5 links from the E mark on the exhaust sprocket to the I mark on the inlet sprocket.
This all has to be done with a mirror as seeing it is impossible. Mine looked like 4.5 but the (a) mark was well out of sight down in the head. Obviously the mechanic missed this and relied on the 4.5 links.
Anyway..I put it right and it’s like a new bike. It pulls like a freight train up top and is actually fast enough to scare me The stumble is gone and I have some fuel economy back.
My advice would be to get an unknown bike onto the dyno if you ever get the chance as it might show up a problem that you had no idea existed.
Finally got around to booking my S10 into the Power Commander tuning shop in Ashburton New Zealand.
The bike has had a mid range stumble ever since I have owned it. I have spent countless hours testing coils and every other sensor the bike has trying to find the reason. I have had it since 60,000ks and it now has 87,000ks.
It has a full arrow exhaust, Uni air filters and a PC5 to adjust the fueling accordingly.
The guy that runs the shop is a Guru with PC.
He did some warm up runs towards 3/4 throttle and noted the air fuel ratio (AFR) was slightly rich but said it was acceptable and wouldn’t cause a stumble.
Then he did a full power run right out to 7,750rpm. It filled his dyno room with black smoke and when all that had cleared he shut it down and told me I had a turtle.
The bike made 78.5 HP and 45 ft/lb of torque!
The AFR went off the scale below 10.0. He took -20 off the 100% range and tried again. He managed to get 82 Hp out of it without the smoke this time.
After pulling up a previous S10 that ran 102HP completely stock on his screen we both came to the conclusion it either had no compression or the valve timing was out. Pulling 20% fuel out of a stock ECU map to get an acceptable AFR meant something was wrong.
Now I have ridden this bike for 18 months thinking the whole time it was fairly lazy but the 260kgs was the reason.I rode it home and pulled it apart.
Going straight to the camshaft timing I found the inlet cam was retarded by a tooth!
I’m guessing the bike hasn’t been right since it’s 40,000k valve adjustment... a test ride wouldn’t necessarily show it up unless the rider went WOT and thought it was lacking.
I did the 80,000k valve check and it was in tolerance so no adjustment necessary and no I didn’t check the valve timing
The tricky bit is the manual states to line up the exhaust cam and then count 4.5 links from the E mark on the exhaust sprocket to the I mark on the inlet sprocket.
This all has to be done with a mirror as seeing it is impossible. Mine looked like 4.5 but the (a) mark was well out of sight down in the head. Obviously the mechanic missed this and relied on the 4.5 links.
Anyway..I put it right and it’s like a new bike. It pulls like a freight train up top and is actually fast enough to scare me
The stumble is gone and I have some fuel economy back. My advice would be to get an unknown bike onto the dyno if you ever get the chance as it might show up a problem that you had no idea existed.
