Post by wayne on Mar 9, 2021 22:41:17 GMT -5
How do you test the RE5's compression and what should you expect ?
Have a look at the following made by member JESS. It demonstrates both the use of the genuine Suzuki compression tester and a standard 2/4 stroke gauge.
Following the video are general guidelines with regard to compression reproduced from elsewhere on the board. These are opinions but would be generally accepted.
NOTE: when cranking the engine, open the throttle fully.
Here's a broad guideline on what compression can mean if you're looking at purchasing a bike. If you already own one, read this in conjunction with Jess's notes about bikes showing less than 100 psi below. Don't throw it away yet.
I've seen readings over 140 which are possibly due to tester variations (theoretical maximum compression as noted by Jess below is 138.18 at sea level). They are very rare. One in particular was outstanding and backed it up on the dyno by achieving nearly 50 hp at the rear wheel. Ten percent more power than the next-best we tested and about 5% more than a demo bike dyno'd back in the day. Jess ranked it as one of the top 5 bikes he'd ever ridden.
Brand new engines, as Jess demonstrates, should give you something around or over 130 but these do improve once run in.
Old engines that have sat around for while, in my limited experience, will free up and improve their compression after a few hundred miles.
NB: As Jess notes having all three lobes giving similar compression can be more important than the peak reading of any one lobe. See below for some comparison traces.
Very good > 130 psi
Good >120 psi
Acceptable > 110 psi
Borderline > 100 psi
Forget it < 100 psi
In practice, it's pretty hard to pick the difference between the 120 and 130 category, they're all good performers. Bikes in the 110 to 120 bracket are still good riders and it would take some experience to notice the practical difference. Below 110, the loss of power is noticeable but I've got one which will still indicate at least 160 kph (on the standard, optimistic speedo).
By comparison, here's some actual compression readings from the life of a regularly ridden RE5 done by a dealership:
First service at 1200 klms - 138
At service 42,000 klms - 134.5
At service 64,000 klms - 116
EDIT: re the above. I wonder what happened between 42 and 64,000 klm? A trace from one of our RE5 Experts (TIMPA) with a 60,000 klm (37,353 miles) bike shows around 133 to 135 psi with smooth peaks. So, well looked after, you can do better:
COMPRESSION ACROSS LOBES
See the two traces below. Ignore the total compression, look at the spread of compression between the 3 lobes. The top trace is about as good as you'll get. The lower trace more pronounced in its spread. The manual says that the maximum acceptable difference between lowest and highest is 7 psi. Mazda blokes have told me 10% is a reasonable guide. I've got one with lobes well outside the manual's limits and just beyond the mechanic's limits (104/108/116) and other than a fraction more vibration than others, you wouldn't really know.
Have a look at the following made by member JESS. It demonstrates both the use of the genuine Suzuki compression tester and a standard 2/4 stroke gauge.
Following the video are general guidelines with regard to compression reproduced from elsewhere on the board. These are opinions but would be generally accepted.
NOTE: when cranking the engine, open the throttle fully.
Here's a broad guideline on what compression can mean if you're looking at purchasing a bike. If you already own one, read this in conjunction with Jess's notes about bikes showing less than 100 psi below. Don't throw it away yet.
I've seen readings over 140 which are possibly due to tester variations (theoretical maximum compression as noted by Jess below is 138.18 at sea level). They are very rare. One in particular was outstanding and backed it up on the dyno by achieving nearly 50 hp at the rear wheel. Ten percent more power than the next-best we tested and about 5% more than a demo bike dyno'd back in the day. Jess ranked it as one of the top 5 bikes he'd ever ridden.
Brand new engines, as Jess demonstrates, should give you something around or over 130 but these do improve once run in.
Old engines that have sat around for while, in my limited experience, will free up and improve their compression after a few hundred miles.
NB: As Jess notes having all three lobes giving similar compression can be more important than the peak reading of any one lobe. See below for some comparison traces.
Very good > 130 psi
Good >120 psi
Acceptable > 110 psi
Borderline > 100 psi
Forget it < 100 psi
In practice, it's pretty hard to pick the difference between the 120 and 130 category, they're all good performers. Bikes in the 110 to 120 bracket are still good riders and it would take some experience to notice the practical difference. Below 110, the loss of power is noticeable but I've got one which will still indicate at least 160 kph (on the standard, optimistic speedo).
By comparison, here's some actual compression readings from the life of a regularly ridden RE5 done by a dealership:
First service at 1200 klms - 138
At service 42,000 klms - 134.5
At service 64,000 klms - 116
EDIT: re the above. I wonder what happened between 42 and 64,000 klm? A trace from one of our RE5 Experts (TIMPA) with a 60,000 klm (37,353 miles) bike shows around 133 to 135 psi with smooth peaks. So, well looked after, you can do better:
COMPRESSION ACROSS LOBES
See the two traces below. Ignore the total compression, look at the spread of compression between the 3 lobes. The top trace is about as good as you'll get. The lower trace more pronounced in its spread. The manual says that the maximum acceptable difference between lowest and highest is 7 psi. Mazda blokes have told me 10% is a reasonable guide. I've got one with lobes well outside the manual's limits and just beyond the mechanic's limits (104/108/116) and other than a fraction more vibration than others, you wouldn't really know.