Sizzling over 40mph

I have the R4F 7.5 hp motor (used) and 98v. I am hearing a bit of a sizzle over 40mph. Electric sizzle from the motor for sure. Granted, I am pushing things waaaay too hard, but has anybody else experienced this?
Clearly, this is a limit I should not push past as grenading the motor scares the beejeezus out of me. I was just wondering if it might be a controller code mistake.

I think all you hotrodders need techs. Very simple to do.
4 pulses/rev. So a v8 tach should read correctly.
I use a cheap led counter from ebay.

That confused me for a bit until I processed it.

You are telling me to put a tach on my GEM so I can make sure I’m not going “way the ■■■■ over” the suggested RPMS of the motor.

Good call. I’ll do that post haste.

Im interested in this Matt, let me know what you come up with. My blue motor gets way hot! Im going to start looking tonight.

Hit it with a laser temp gauge to find out how hot. The blue ones are fine running into the 200-250f range.

I need to make a Harbor Freight run tomorrow. I hear their laser temp gauges actually arent bad. After a hard run, you cant touch my motor. Also hear that sizzle too, I think its the brushes cooking :hot_face:

Heat and rpm are different issues. Over speed can lose brush contact and proper commutation.

I can give you a link to the one I use, or send it out to copy.
The 12v line from controller has trouble supplying enough current for the leds. I use a 9v battery to power the tach. Do not tie into 12v system. Sparks will fly.
May be this one.

Rodney didn’t like it. Too much resolution. That can be programmed out.
Program for speedometer if you like.
I may have a few if you don’t want to wait for China.

If you run a bms. Use one of the temp sensors in the motor.
If you ever have motor apart, stick it on the field coil.

Temp in upper left. 39C can change to F.

Matt , raise your minimum field current (#7) this will reduce the Armature amps at high rpm and help the motor stay cooler . Also running higher tire pressure will reduce rolling resistance and your motor will be happier . I did a test with tire pressure on a lead Gem and increasing to 35psi added 2 miles per hour on the big end , that’s a lot .

I have a interactive spread sheet that gives RPM at up to 40 MPH for all transmission ratios. Just enter tire diameter on your cart and it tells you motor RPM. email me

If your hearing a sizzle your motor needs service. Brushes are sticking and/or commutator needs resurfacing. If you continue to drive it you will burn it up. I service a dozen motors a year most for this condition.

Matt what your talking about I have Dubbed
“Commentator Buzz” it sounds like a sizzle YES. It’s straight up lightning/sparks between the Brushes & the commutator. When I would hear it I back off. It’s when I was pushing the motor hard.

I appreciate everybody’s advice. I ended up doing what Grant just described…backing off a bit. Everything feels great until I pass 41, and at that point I’m already going far too fast so why bother? It’s not as if I’m at Bonneville Salt Flats trying to set a GEM land speed record. I go 1.5 miles to the grocery store and 1.5 miles back with 10 stop signs.

It would be cool to take the chrome screen that go’s around the motor off and place a go pro pointed into the motor and go for a Sizzler Ride. I would like to see what’s going on? I’m guessing it’s a bunch of blue sparks and crazy ness

I think you are right. When I initially put the motor on she was on jack stands so I gave it a few revs to make sure things worked. I stood up and could definitely see blue sparks.
Hopefully, I have tuned all that out now. If not I can already imagine Rodney chuckling and saying “I told him so, damned kids” while cashing my check.

That’s a solid tip. I had to do a lot of brake work when I got it initially.
I gotta pull the back spat and boot boot off here soon anyhow to put in those hood pins. I’ll give it a check. :100:

This is very interesting. I installed a used blue motor this year and now I have that sound. I was thinking it was coming from the contactor and that it was going bad. Now I’m wondering if it is the motor. I’ll have to check it tonight. I only get it when I’m under a heavy load. Speed seems to be less an issue as load. I will usually back oft the throttle when it happens and it goes away.
Is this a sign that the motor needs repair or is it a condition of over stressing the motor? I definitely don’t want to burn it up!

Your motor needs service NOW !!!.


Talk to me Rodney. What do I need to do? Are the brushes sticking or worn or what am I looking for?

Probably also commutator could need turning.

In a message dated 7/19/2019 10:18:45 AM Eastern Standard Time, writes:

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Hey Matt: why don’t you try a quick trick.
Take the hood off (should only take you 1 second) remove the chrome screen around the motor. Jack your car up and have someone run the motor as you spray some electrical cleaner threw the motor. I’m sure it’s not as good as cleaning the brushes by removing them but it would be cool to see if this makes a difference. My advise is Alwasy run a few cans of electrical cleaner threw any used motor your installing.

In the past I have started with blowing compressed air threw the motor. Is usually a huge black cloud comes flying out.

Then I remove and clean the brushes with a lady’s nail file. The squarer brush holders usually need a good cleaning/sanding.

I have never turned the Com, I just use the electrical cleaning brush on the com and then run electrical cleaning spray threw everything and put it back together.

Just becarefull of the brush holder head. It’s made from a non conductive composite material like plastic and fiberglass mixed together if you torque on the brushes the wrong way you can break the holder and then your in for a $70-100 part.