Speedo vs Tach

[tBill]

Noob here. I apologize if this has been discussed somewhere else but I couldn't find anything. I recently acquired an '89 VR that's been triked. Old barn find with only 81,000 miles! Plugs, fluids and lots of TLC and it's running now but still needs the carbs synced. I've determined that the speedo is fast by 5 - 7 mph at road speed, but from reading the forum posts, that sounds pretty normal. I'm not sure the diff ratio is proper. What speed should I be showing at 4000 rpm? It's indicating around 63-65 which is actually a bit shy of 60. That's comfortable but can get you run over in traffic!

 

The fuel mileage has been awful but is improving with a couple of cans of Seafoam and about 500 miles under the tires. Last fill-up, I got right at 30 mpg. Still idling at 1200-1300 after it warms up. That seems high to me.

 

Any ideas and suggestions will be greatly appreciated.

[bongobobny]

First off welcome aboard!

 

Yah, the speedo reads high on our bikes. You could correct it in your case by going to a slightly larger size front tire as the speedometer drive is off the front wheel. The RPM's for 60mph sounds quite high, that is going to be the function of your rear end ratio. You have to remember that by triking the bike it added a lot of weight to the bike and it effects the overall performance. You will never make 40 mpg or even close. More like 32 mpg.

 

Idle speed should be around 900 to 1000 RPM. I pretty much guarantee your carbs need rebuilding and proper setting up from setting for so long. Seafoam will help some but it is not a cure all silver bullet either. First thing to look at would be your diaphragms for pinholes but that is only the beginning...

[Venturous Randy]

Actually, you have several different issues here. Given the bike has been triked, you probably do not know what the differential ratio is, so doing a comparison with a stock Venture won't work in comparing RPM's to speed unless you learn the rearend ratio and compare it to stock.

As far as 1st gen speedometer accuracy, to my knowledge, they are not nearly as far off as 2nd gens. On my 83, my first speedometer was very close. When I replaced it, the other one was a bit off. In the following, from another post, I described how I corrected it but it was to another member's problem.

 

First, your speedo runs off your front wheel.

I did this on my 1st gen years ago and it is off 1 mph at 70 mph according to my GPS.

The way I did it was to determine how far it is off in distance from being right (and in your case we will say it is 1/4 inch too much counter clockwise). I then removed the speedo and lifted the needle over the stop pin. I moved the needle several times and let it come back to the natural point it would stop. Once I was comfortable with that point, I marked it on the face.

I then gently pulled the needle off with some curved needle nose pliers and repositioned the needle back on the pin the distance I first measured it being off( and in your case to be moved 1/4 inch clockwise). Again, I moved the needle and let it go back to its natural resting place to determine if it was where I wanted it. Once I was comfortable with where it was, I gently pecked the needle tighter. I then placed the needle on the correct side of the stop pin.

RandyA

[bongobobny]

There ya go!! Use your GPS for a speedometer!

 

From what I remember, my speedometer read around 65 when my GPS said 60...

[tBill]

I appreciate it. Pretty much as I expected. I did manage to get the idle down. Throttle was sticking a bit. Cleaned everything up and now it's doing better. I intend to order kits for the carbs and tackle that next.

 

This trike set-up is really quite heavy. No fiberglass. It's all metal and appears to have been shop built out of left over tank parts! It has a complete rear suspension out of some car including the independent suspension and differential. I'm sure the final ratio is a bit high (numerically) but that probably helps with the weight issue. The old bike performs well and rides like an old, heavy Cadillac!

 

Thanks again,

[bongobobny]

Interesting!!! The only 1st gen kit I knew of was/is Triwing but they are solid axle and fiberglass body. Yours must be a custom fabrication job. I am considering triking my 1st gen but would love IRS...

[tBill]

Well, everything is going really well. Got all the minor TLC stuff done. It now runs beautifully and has amazing power and acceleration for what it is. We figured out that the differential and independent suspension came out of one of the little jap trucks! A guy that was looking at it recognized it because he has one of those trucks.

 

Changed all the fluids again this week and installed full synthetic. That made an amazing difference. Everything quieted down and the engine is so smooth that you can't hear it running except for the exhaust!

 

Thanks for your help!

[bongobobny]

Waaaay cool!!!