81 1200 Project

[brianinpa]

Well it wasn't the timing being off, or the C5 wheel being loose.

It's amazing what a new pair of spark plugs will do...

Now I need to put everything back together, ride it and see if I foul these plugs.

 

[backlander]

The list of possibilities gets smaller !!

 

[slabghost]

Were the plugs oil or gas fouled? Or just faulty plugs?

 

[brianinpa]

Not sure. When I pulled them out, they were black. I took the plugs from my 84 and put them in and it fired right up.

I was thinking the carb was jetted correctly for idle and needed a little more jetting for full throttle and that is what I was going to be working on when I ran into this problem. Now I am going to rethink my idle jetting.

 

[slabghost]

If it seemed a dry black it was probably way rich.

 

[joedrum]

i agree idle jetting to big id say ...rich idle leads to black fouling plugs ...im not sure where 5string is at on idle jet ...but oof hand im thinking 40 jet is about all that can be use and not be ric ....oh and by the way ...the one thing i forgot to bring on the trip was your number ...

 

[brianinpa]

Well Joe, I just PMed you my number again.

 

[brianinpa]

I was able to get about a 5 mile ride on it tonight without any major problems. There's a slight hesitation that I need to work on, but I have a few other things to work on first... Brakes, water temp gauge isn't working (and that is something I really want working), cleaning up some wiring issues, etc., etc., etc...

But, it's nice to know that I have a bike I can jump up if I want to get away.

 

[fivestring]

Glad to hear you can get some seat time.

On my hesitation problem, I just discovered last night I was getting too much accelerator pump. I had a minor bog off idle with the accelerator pump at 3/4. I turned it up all the way and had trouble even getting the bike to take off from idle or when turning a corner and trying to accelerate. It just wanted to fall on it's face. I came back to the shop and backed the pump adjustment down to 1/4. Huge improvement! It made it easier to go from a dead stop without blipping the throttle multiple times to get rolling. I'm going to try it again at the minimum accelerator setting to see what that is like.

My settings are: idle jet drilled to .60mm, main jet 142, air screw 3.5 turns. My plugs are perfect color according to our resident gurus so I think I'm pretty close to fully dialed in right now.

 

[brianinpa]

Good to know. I want to start some fine adjustments on the carb, but I need to bleed the rear brake first.

The 1200 brake caliper is in close proximity to the 1100 saddlebag crash guard so getting the brake bled completely is a challenge. I need change the routing of the brake line to do it, but first I must convince the saddlebag crash guard that it needs to move...

 

[joedrum]

seemsi remember dans set up he not using accelleraror pump at all on his solex jeep carb....69 idle jet seems big 5string ,,,but your plugs look lean really ....but the bog with accellerator pump peoves it quite rich there .....there is rhe possible smaller idle jet and more accellerator pump deal working as good or better

 

[dan filipi]

joedrum » 7 minutes ago[/url]":3y8on66d]
seemsi remember dans set up he not using accelleraror pump at all on his solex jeep carb....69 idle jet seems big 5string ,,,but your plugs look lean really ....but the bog with accellerator pump peoves it quite rich there .....there is rhe possible smaller idle jet and more accellerator pump deal working as good or better

That's right, no accelerator pump juice on mine.
Seems there is a lot of variation in how these carbs will run.

I think we're hijacking Brian's thread. Sorry Brian.

 

[fivestring]

Agreed. I don't want to hijack but maybe he can use the info to help dial in, so...

Joe and Dan have a good point. There are probably several different jet/pump setting combos that will work well. I can imagine Brian staying smaller on idle jet size and bumping pump to get smooth response while I am at larger jet/smaller pump. If the rest of the throttle band is responding well then ok. If I find a lack in higher end flogging inputs, I may want that big squirt back. Or maybe I'll end up with no pump too. More testing and tuning ahead!

 

[brianinpa]

Hi-jacking a thread... that never happens here, especially on a thread that is 24 pages long. :shock: :smilie_happy:

Anyway, I hate to think that I have been scratching my head for so long with this carb/engine configuration when the problem may have been bad plugs that looked good, but it is beginning to look that way. I had the accel pump disconnected and it is now reconnected. I think I am going to leave it connected because I do not think the electric choke is working on my carb, so I like the fact that I can give the carb an extra squirt of fuel to get the motor started. Once it is started, I can lock the throttle at a higher rev until the motor warms up a little.

I soldered the idle jet and started small and have slowly worked my way back up to the stock opening, so as of fight now, my carb is completely stock. I have to look back through these 24 pages to find what those numbers are.

 

[joedrum]

great work guys ....we are really learning this carb now ...

 

[fivestring]

If yours is the same as mine, Brian, you should have had a .55 stock idle jet. I am one step bigger at .60.

 

[brianinpa]

Yes, I think it is a .55 idle and 1.275 main.

 

[brianinpa]

Rode it again this evening for about 10 miles. The temp needle never came off of cold, so that is the first thing I am looking at tomorrow. After that, I need to get the motor warmed up and get the idle RPM set because I am pretty sure the idle jet is good. I have no stumbling at all when pulling out or running slow. The area that seems to be the problem is higher RPMs. The motor just seems to hesitate when I get up around 65 MPH in the higher gears.

In 1st thru 3rd, it pulls hard and I am quickly up against the C5 rev limiter (I keep forgetting that it is there until I hit it) so I go from 0 to hold on tight in a hurry.

After riding the 84 for so long, riding the 81 feels like a new bike again.

 

[fivestring]

Do you have stock exhaust pipes?

Try going up to around 135-140 main jet. It will make you smile.

 

[brianinpa]

Yeah, stock pipes. I made an adjustment on the acel pump that just didn't make me happy, so that is getting undone, and the main jet size is next.