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Rostra cruise control mystery

Rostra cruise control mystery

Rostra cruise control mystery

My problem:
I have installed the "Rostra" aftermarket cruise control in both my street rod that I built and my motorcycle.
Either unit works perfectly in the street rod. But when installed on my motorcycle here is what happens:
It randomly works when I first fire it up. Usually (not always) it works fine until I come to a stop. Then (most of the time) it wont lock up again... until I (1)come to complete stop and (2) turn the motor off and back on. Then it will(usually) lock up (as many times as I like) until I come to a stop again. Anything other than doing the two steps outlined above wont reset it.
The only difference between the street rod and the motor cycle is... the street rod has a 4L60-e transmission and I use the VSS signal for speed input. The motor cycle has no VSS unit so I mounted 2 magnets on the rear wheel along with Rostra's coil pick up. And of course, I select the proper pin switch positions for that configuration. Again, when it works, it works great.
I have gone over the harness too many times to count and anyway I don't see how it could be a wiring problem since it does work some of the time. It can't be the unit itself since both work fine in the street rod.
For some reason the engine has to be turned off/on while the rear wheel is stationary to get a good reset. That's what has me stumped.
(Rostra customer service wont talk to me when they find out the unit is installed in a motorcycle).

RE: Rostra cruise control mystery

Are you getting a clean (and uninterrupted) signal from the mag sensors on the motorcycle? If the magnets are too far away to detect on occasion, that may throw the unit off as it expects a pulse within a certain time period and doesn't see one.

Dan - Owner

RE: Rostra cruise control mystery

A lot of motorcycles have pretty poor voltage regulation compared to most cars. Voltage at idle may drop enough that it goes into a lock out until power is cycled.


The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

RE: Rostra cruise control mystery

I know on that system the brake switch wire requires a fairly low resistance to ground. It expects a couple of tail lights that are only a few ohms of resistance when cold between the wire and ground.

RE: Rostra cruise control mystery


Below is an image of one of the mounts I fab'd for the magnets. The manual says to use 2 on a front wheel drive car which would equate to a motorcycle rear wheel. I have tried both 2 and 3 magnets. No difference, no change. I would not know how to check for a 'clean signal' but the magnets all have about the same amount of attraction and pass the coil within about 3/8th of an inch.

I have checked voltage several times with pretty much the same result each time... never drops below 12.2 at low idle. Typically shows around 14.4 at higher rpm.
That said, I have even placed a spare (fully charged) M.C. battery in a saddle bag and hooked up the cruise control to it with nothing else hooked up to it. Same result.

I have added a relay so that when the brake circuit is energized, the 30-87 pins close from a ground wire secured directly to the negative battery post to the proper CC wire.

Thanks for the suggestions!

RE: Rostra cruise control mystery

3/8" sounds like a very big gap for these to work but if it does on startup I would not think that's the problem. If you have a scope you can put the bike on a secure stand and run it with the wheel off the ground and look at the signal.


The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

RE: Rostra cruise control mystery

First, thank you guys for taking the time to post and offer advice. But here is what happened. Someone who knows more about electricity than I do suggested I use a 'noise filter'. Very skeptically I researched what I could find on Amazon. Since I had little to no faith this could solve my problem I opted to read the posts on a cheap (7bucks) litte (little is good, after all it IS a motorcycle) filter known as the 'AX-ANR1000'. One post really got my attention. He had installed a radar detector on a motorcyclist but he got way to many false positives until he installed this filter. Hmmm. So I picked one up, installed it today and just got back from an exhaustive test. YES! I could not make it fail!
I certainly don't understand why it fixed it (given the sequence of events required to get it working previously) but at this point I guess I don't really care since IT WORKS!

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