final inspection - tune?

[hotrdd]

So where I live in Calgary you need to do an "out of province" inspection when you bring a new vehicle into the province. I brought my bike in for the inspection and everything is looking good except it won't pass the inspection because it's running rough and back firing. The predicament is that i can't drive the bike until it passes the inspection, but I can't tune the bike without driving it. The shop rate for a dyno tune is $150hr. So I have a couple questions.

1976, open exhaust and intakes with Boyer Ignition.

1) what would you do?
2) can you re-jet the Carbs without pulling them? Or is It just easier to pull them? I'd hate to have to pay for 4+ hrs of tuning.
3) I'm running open intake and exhaust and the shop suggests that he would start by going 4 up from stock. Thoughts.

 

[XSLeo]

Four up is a big step. With uni-filters and a low resistance exhaust I'm one up on the pilots and two up on the mains. 1 3/4 turns out on mix screws. Start there, and test ride it.
www.amckayltd.com/carbguide.pdf might help.
If you live in town then the testing might be a bit tough. Do you have a friend out in the country? Take the bike there and test it.
On the jets, you might find a local shop that works on dirt bikes and such with an assortment of gently used jets in a bin. Take the bike there. You might get to try different jets and only pay for the ones you actually use.
If not just buy an assortment of jets from stock up two on the pilots and up two or three on the mains. Test with one up on both. The testing procedure is in the carb guide. If that works your good if not try another step on the mains.
There is no set recipe for jets, it takes a bit if experementing. What works on mine may not work on yours, every bike is a law unto itself.
You can change the main jets by just removing the drain plug on the bottom of the float bowl. The pilots, you need to remove the float bowl. Kinda tough unless you have swapped the phillips head screws for allen heads.
I would pull the carbs and give them a good cleaning, they probably need it too.
The carb guide helps on that too.
Leo

 

[hotrdd]

The Carbs are clean and I did go one up on the mains and pilots before I threw things back together. Because I don't have a truck or trailer tacking is thing tothe country isn't easy. I thought I actually had the bike pretty close but the mechanic was less than positive about it.

 

[5twins]

If the carbs are the original '76 set then they came with the smallest main ever put in a 650, a 122.5. Yes, most of the other carb sets like 1 to 3 steps up on the mains but yours may need more because of that small original size. You may need mains somewhere in the low to mid 130s, 4 or 5 sizes up. I would try 132.5s, one up on the pilots, and needles leaned one step to slot #2. That's what worked on mine with pods and the Commando mufflers but your open exhaust may require even more on the mains, like a 135 or 137.5. As Leo said, experimenting is the only way to know for sure.

You shouldn't need to ride the bike to get it closer than it is now. You should be able to tune the popping out of it with it just running in the driveway. Final exact main jet selection will take some road testing but you should be able to get it close enough to stop backfiring through just stationary testing. Bottom line is I don't think just one size up on the mains is enough for that carb set.

 

[ProSimex]

Go to a different shop. My would barely start and I got it safetied in ontario. Lights worked, brakes good, frame good ect..

 

[hotrdd]

I'm heading tothe shop tomorrow to have a chat and see what we can work out. Needles have already been moved to the second slot and the pilots have been moved up one so maybe I can just have them leave the Carbs on the bike and change the mains. I have a feeling the majority of what I would be paying for is the time to put them on and off again..

 

[junkshow]

Why not make these changes yourself? Part of the fun of owning these old bikes is working on them yourself. You get to know the bIke from the inside out. Laterally.

Posted via Mobile

 

[hotrdd]

I would love to do this myself but the problem is that I have to borrow a truck or trailer ever time I move the bike and there isn't anywhere for me to ride it to test the tune. I've already taken it around the block a few time without plates and it seemed to be fine. The other issue is that I have a short window to finish all this or I have to pay another $160 for another inspection. But before I take this home I'm just wondering if this is something I should be able to do in the garage. If I blocked the bike up on my stand would it be stupid to let the rear wheel free spin and try to tune that way or is this stupid and wouldn't help without a load on the drive wheel?

 

[5twins]

As I said, you should be able to tune it quite close in your garage. Tuning with the bike "at rest" is the 1st step in the tuning process. For final and fine tuning, you will need to ride it but you should be able to get it close enough to pass inspection just tuning in your garage.

You don't need to elevate the rear wheel and put it in gear. Just do throttle blips and roll-ons. Note how the engine responds to the blips and how quickly it drops back down to idle - and tune accordingly. Roll on the throttle and run the RPMs up to 3 or 4K, hold it there momentarily, and look for smooth running (good) or break-ups (bad). Note how the motor transitions from idle or just off idle into the midrange.