Using old style Tach gauge to check RPM - Snowblower Forum : Snow Blower Forums
 
LinkBack Thread Tools
post #1 of 7 Old 02-28-2015, 09:29 AM Thread Starter
Senior Member
 
tpenfield's Avatar
 
Join Date: Feb 2015
Location: Massachusetts
Posts: 1,080
Post Thanks / Like
Thanks (Given): 48
Thanks (Received): 60
Likes (Given): 131
Likes (Received): 221
Garage
Using old style Tach gauge to check RPM

I have an old 1980's vintage tach/dwell gauge and wanted to use it to check the Maximum RPM on my Troy-Bilt 2410 snowblower. It is the kind of tach that has a clip that surrounds the spark plug wire.

It did not seem to get a signal, when checking the RPM. . . very erratic.

Soooo, I took out my old Toro 521 and checked the tach gauge . . . it works !!! The Toro maxes out at 3800 RPM. Idles at about 1400 RPM.

I am wondering if there is something 'special' about the ignition/spark plug wire on the newer machines that shields the magnetic field on the wire? Is there a different way of checking the RPM?

TIA for any assistance.
tpenfield is offline  
Sponsored Links
Advertisement
 
post #2 of 7 Old 02-28-2015, 09:43 AM
Senior Member
 
Join Date: Mar 2014
Location: Albany, New York
Posts: 1,741
Post Thanks / Like
Thanks (Given): 231
Thanks (Received): 199
Likes (Given): 2045
Likes (Received): 517
Quote:
Originally Posted by tpenfield View Post
I have an old 1980's vintage tach/dwell gauge and wanted to use it to check the Maximum RPM on my Troy-Bilt 2410 snowblower. It is the kind of tach that has a clip that surrounds the spark plug wire.

It did not seem to get a signal, when checking the RPM. . . very erratic.

Soooo, I took out my old Toro 521 and checked the tach gauge . . . it works !!! The Toro maxes out at 3800 RPM. Idles at about 1400 RPM.

I am wondering if there is something 'special' about the ignition/spark plug wire on the newer machines that shields the magnetic field on the wire? Is there a different way of checking the RPM?

TIA for any assistance.
I don't know enough about those old tachs to comment on why it's not working with the old machine...maybe the pulse width is too different on the newer machine? Is the old 521 a points ignition?

Regardless, maybe grab yourself one of these new


and mount it permanently on your blower.

Then double-check the RPMs on that old 521...3800 is revving a bit high (3600 Max; measure when warm) if your old tach is accurate...1400 is on the low side but if it's idling steady, then leave good-enough alone. Most old tec idles are set around 2k.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
('89 Toro 824)

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
('70 Allis-Chalmers Tracker-7)

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
('80 Toro 724)

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
('71 Ariens 910965 SnoThro 524)

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
('87 Toro 38150 826)

Last edited by classiccat; 02-28-2015 at 10:01 AM.
classiccat is offline  
post #3 of 7 Old 02-28-2015, 10:00 AM
Senior Member
 
Join Date: Oct 2014
Location: garden state
Posts: 105
Post Thanks / Like
Thanks (Given): 0
Thanks (Received): 3
Likes (Given): 0
Likes (Received): 9
I have an old Sear's Craftsman tach/dwell meter from 1972. It has settings for 4/6/8 cylinder engines. I think the snow blower being 1 a cylinder engine causes erroneous readings. Also it looks like the spark plug wire on the snow blower might be better shielded than older automotive spark plug wires causing inductive pick up problems for the tach.

Whimsey
whimsey is offline  
post #4 of 7 Old 02-28-2015, 10:38 AM Thread Starter
Senior Member
 
tpenfield's Avatar
 
Join Date: Feb 2015
Location: Massachusetts
Posts: 1,080
Post Thanks / Like
Thanks (Given): 48
Thanks (Received): 60
Likes (Given): 131
Likes (Received): 221
Garage
Yea, this is a dwell/RPM gauge that is designed to go on the spark plug wire rather than the ignition wire to a distributor.

It has settings for '2 cycle' vs '4 cycle' and then a separate slide switch for 'low' rpm, 'high' rpm, and dwell. So, it should work regardless of the number of cylinders.

It works great on the old machine. . .

Does not work on the new machine. . .

So, maybe the ignition wire on the new is shielded and the newer gauges/meter are more sensitive.
tpenfield is offline  
post #5 of 7 Old 02-28-2015, 10:39 AM
Senior Member
 
Join Date: Jan 2015
Location: Connecticut
Posts: 125
Post Thanks / Like
Thanks (Given): 15
Thanks (Received): 9
Likes (Given): 1
Likes (Received): 14
Quote:
Originally Posted by tpenfield View Post
I am wondering if there is something 'special' about the ignition/spark plug wire on the newer machines that shields the magnetic field on the wire? Is there a different way of checking the RPM?

TIA for any assistance.
I would guess that modern ignitions with resistor plugs and/or wires might be suppressed enough that an older tach might not get enough signal. Older ignitions used solid wire and no resistor plugs.

Quote:
Originally Posted by whimsey View Post
I have an old Sear's Craftsman tach/dwell meter from 1972. It has settings for 4/6/8 cylinder engines. I think the snow blower being 1 a cylinder engine causes erroneous readings. Also it looks like the spark plug wire on the snow blower might be better shielded than older automotive spark plug wires causing inductive pick up problems for the tach.

Whimsey
I have one of those, same vintage. You need the coil signal at the points to make em work.

I use an optical non-contact tach. You put a piece of reflective tape on the output shaft and point the laser at it. I use it for my lathe and other tools too. Surprisingly cheap off Amazon.

Craftsman 5/22 with impeller mod & poly skids,
Ariens 28+ Deluxe 921037 AX291
Dave C is offline  
post #6 of 7 Old 02-28-2015, 01:40 PM Thread Starter
Senior Member
 
tpenfield's Avatar
 
Join Date: Feb 2015
Location: Massachusetts
Posts: 1,080
Post Thanks / Like
Thanks (Given): 48
Thanks (Received): 60
Likes (Given): 131
Likes (Received): 221
Garage
UPDATE:

I got it to work finally . . .

I added a few more coil/windings to the inductive sensor clip on my dwell/RPM meter, and set it so the coil was pressed up tight to the spark plug wire. The current must be a lot less through the spark plug wire on the newer machines.

The meter is by "Sun Electric" may be as early as 1970's vintage, probably 1980's.

I got 3800 RPM out of the new machine (Troy Bilt 2410), which is a tad high vs. the engine spec is 3600, I believe, . . . so I tweaked the throttle setting back a bit.

The old Toro (521) was 3800 RPM, and it has been that way forever, so I left it alone
tpenfield is offline  
post #7 of 7 Old 02-28-2015, 01:55 PM Thread Starter
Senior Member
 
tpenfield's Avatar
 
Join Date: Feb 2015
Location: Massachusetts
Posts: 1,080
Post Thanks / Like
Thanks (Given): 48
Thanks (Received): 60
Likes (Given): 131
Likes (Received): 221
Garage
FWIW - here is a picture of my Inductive dwell/tach meter. Click on image icon to see bigger view.

Using old style Tach gauge to check RPM-suntunecp7602.jpg

Came with a timing light as well. Probably have not used it in 20+ years.

Last edited by tpenfield; 02-28-2015 at 01:59 PM.
tpenfield is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Snowblower Forum : Snow Blower Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome