Coil for 1972 CB175
- Thread starter Lucas Denton
- Start date
yamahaggard
New Member
I have yet to try it which is prolly no help, but I used a Accel Harley supercoil its the 3.0-3.5 ohm setup. I had to modify the frame a bit to make room for the slightly bigger coil. I got the idea from another forum. Here's the link http://www.hondatwins.net/forum/viewtopic.php?f=18&t=3812
hope this helps
hope this helps
Redliner
Over 1,000 Posts
There are NEW Yamaha coils online for $25 each shipped.
All you have to do is rig up a mount (the bolts must be grounded to frame) then fiddle with the wiring and go. The difference is really noticeable.
Before doing so, test your coil and boot.
Put an ohmeter in both ends your spark plug boot. It should not be much higher than 5kΩ. If it is higher, just get an NGK 5kΩ boot and throw it on, see if that helps.
To test your spark, put a clean spark plug (clean the anode and ground strap with sandpaper or use a new one) into your spark boot. No need to pull yours from your engine.
Place the plug so that the threads rest against the engine somehow and offer about a half-inch gap from the ground strap and anode.
Remove your points plate cover. Now turn the ignition switch to on and open and close the point that connects to the coil you're testing. As you open it, you see the condition of your spark. Ideally you want a fat blue spark, but a purple one with an obvious flare (v-shaped) is good enough to keep any engine running fine. As long as you see no hint of yellow/orange and it's nit a wispy little spark, that coil is fine.
Move onto the other coil and repeat with the same plug. Don't leave the ignition on for long! It's going to cook your coils!
With the Yamaha coils (you want CM11-50) you will normally have an orange and brown wire. Connect the black from the harness to the orange wire. Reversing this heats up the coils and is inefficient.
All you have to do is rig up a mount (the bolts must be grounded to frame) then fiddle with the wiring and go. The difference is really noticeable.
Before doing so, test your coil and boot.
Put an ohmeter in both ends your spark plug boot. It should not be much higher than 5kΩ. If it is higher, just get an NGK 5kΩ boot and throw it on, see if that helps.
To test your spark, put a clean spark plug (clean the anode and ground strap with sandpaper or use a new one) into your spark boot. No need to pull yours from your engine.
Place the plug so that the threads rest against the engine somehow and offer about a half-inch gap from the ground strap and anode.
Remove your points plate cover. Now turn the ignition switch to on and open and close the point that connects to the coil you're testing. As you open it, you see the condition of your spark. Ideally you want a fat blue spark, but a purple one with an obvious flare (v-shaped) is good enough to keep any engine running fine. As long as you see no hint of yellow/orange and it's nit a wispy little spark, that coil is fine.
Move onto the other coil and repeat with the same plug. Don't leave the ignition on for long! It's going to cook your coils!
With the Yamaha coils (you want CM11-50) you will normally have an orange and brown wire. Connect the black from the harness to the orange wire. Reversing this heats up the coils and is inefficient.
Lucas Denton
New Member
Thanks for all the info guys. I recently bought new boots and spark plugs for it but i will definitely check to see if they are still good. As far as the accel coil what kind of modification are we talking... to the bike or the coil? and also the wires from the coil seem to have a sticky almost tar like substance in them...is this normal or have the wires gotten hot and cooked some kind of insulation surrounding them? another thing i noticed is that there are only like 2 or 3 strands of wire in the cables themselves im sure there should be more. Im new to motorcycles and all the shops around here are Harley Davidson's only or backed up for months so there's no one to really give me any pointers on this speed demon! So i turn to you guys! 
Lucas Denton
New Member
Will try that tomorrow morning! Now i know this is changing subjects...i was doing some things the other day(things that the manual refers to as maintenance) I checked the valves and there was no gap between them so i set them all to the specified gap and it seems really chattery now Im assuming its to much but its exactly what the book said as far as gap. What did i do wrong?
Redliner
Over 1,000 Posts
Better to be too loose than too tight, but noise is no good anyway.
Are you certain that you checked clearances after tightening your adjustment locking nut? And you adjusted each valve at TDC (compression stroke) for each cylinder?
The feeler gauge should just barely drag. Not so much that it's being pinched, just so there is obviously an amount of drag and no slack. Very easy to move with two fingers.
Are you certain that you checked clearances after tightening your adjustment locking nut? And you adjusted each valve at TDC (compression stroke) for each cylinder?
The feeler gauge should just barely drag. Not so much that it's being pinched, just so there is obviously an amount of drag and no slack. Very easy to move with two fingers.
Lucas Denton
New Member
Yes top dead center...and the cb175 fires both pistons at the same time so im guessing all of them should be adjusted to the only t on the startor. I just cant stand all the noise its making i havent ridden it since then out of fear to mess something up!
Redliner
Over 1,000 Posts
Nope.
They fire 360º apart from eachother. Meaning that when they're at TDC, one fires while one is 180º out from TDC, otherwise the exhaust stroke.
If you were able to get ANY clearance while adjusting at the exhaust stroke, that bugger's so damn loose it'll never open those valves.
Take the plugs out and watch inside the cylinder as you spin the engine slowly. If you see the exhaust valve close as you reach TDC, leave it at the T mark and adjust the opposite cylinder. Seeing the valve open and close means it's clearly on the exhaust stroke, 180º from TDC.
Then once you've adjusted the cylinder at TDC, rotate the crank exactly 180º back to the T mark again. This time the opposite cylinder is at TDC and so you can adjust it.
Always always always check clearances after you're done! And only at TDC for each cylinder!
They fire 360º apart from eachother. Meaning that when they're at TDC, one fires while one is 180º out from TDC, otherwise the exhaust stroke.
If you were able to get ANY clearance while adjusting at the exhaust stroke, that bugger's so damn loose it'll never open those valves.
Take the plugs out and watch inside the cylinder as you spin the engine slowly. If you see the exhaust valve close as you reach TDC, leave it at the T mark and adjust the opposite cylinder. Seeing the valve open and close means it's clearly on the exhaust stroke, 180º from TDC.
Then once you've adjusted the cylinder at TDC, rotate the crank exactly 180º back to the T mark again. This time the opposite cylinder is at TDC and so you can adjust it.
Always always always check clearances after you're done! And only at TDC for each cylinder!
Lucas Denton
New Member
So they dont fire at the same time? how does the points work with only one arm inside instead of two? Not my bike just a refrence pic.
Redliner
Over 1,000 Posts
Look up "wasted spark". It fires both spark plugs every time the pistons are at the top, but one is firing while the exhaust is being forced out. There's no loss of power and no real disadvantage to this, since a spark encounters little resistance on an exhaust stroke anyway.
If your cylinders both fired at the same time, and went through the 3 other cycles together without another bang, that engine would rock. I mean that in the worst way
If your cylinders both fired at the same time, and went through the 3 other cycles together without another bang, that engine would rock. I mean that in the worst way
Lucas Denton
New Member
F is for the Firing valves and 180 degrees away there are another set of marks not labeled and that's for the exhaust
Redliner
Over 1,000 Posts
Read what Sonreir says :
Believe me, the cylinders are not at actual TDC at the same time. Why would Honda mark a wheel for the exhaust stroke?
If somehow you still can't believe this, look inside a spark hole and turn the motor until an exhaust valve is open. Leave the engine at this position and check the other cylinder. Do you see an exhaust valve open in that one too?
Believe me, the cylinders are not at actual TDC at the same time. Why would Honda mark a wheel for the exhaust stroke?
If somehow you still can't believe this, look inside a spark hole and turn the motor until an exhaust valve is open. Leave the engine at this position and check the other cylinder. Do you see an exhaust valve open in that one too?
Redliner said:The labeled marks are the timing marks for the left cylinder. The unlabeled marks are for the right cylinder. The first is the idle timing advance mark, followed by the T for TDC mark.
Believe me, the cylinders are not at actual TDC at the same time. Why would Honda mark a wheel for the exhaust stroke?
If somehow you still can't believe this, look inside a spark hole and turn the motor until an exhaust valve is open. Leave the engine at this position and check the other cylinder. Do you see an exhaust valve open in that one too?
Pistons will be a TDC at the same time on a 360° engine. This means the "F" mark is the timing for both cylinders, not just the left. The unlabeled marks are for the timing advance for both cylinders.
Redliner
Over 1,000 Posts
Guh, once he said the marks were 180º apart, I don't know where my mind went. There's no way the advance is 180º away though...right?
Both cylinders reach "TDC" at the same time, but only one is on actual TDC, meaning the top of the compression stroke. At this same time, the opposite cylinder is on the exhaust stroke.
Both cylinders reach "TDC" at the same time, but only one is on actual TDC, meaning the top of the compression stroke. At this same time, the opposite cylinder is on the exhaust stroke.
Redliner
Over 1,000 Posts
According to the shop manual, you adjust one, rotate 360º, then adjust the other.
So it would be advisable that he find which one is on compression, align the T mark, then adjust those valves. Then rotate 360º and adjust the other valves.
Simple, really.
The way that he described it, adjusting both at the same time on the T mark, makes it sound like the adjusted the tappets on one cylinder while they were opening a valve!!!
So it would be advisable that he find which one is on compression, align the T mark, then adjust those valves. Then rotate 360º and adjust the other valves.
Simple, really.
The way that he described it, adjusting both at the same time on the T mark, makes it sound like the adjusted the tappets on one cylinder while they were opening a valve!!!
