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Old 06-28-2011, 07:45 AM   #121
blaine.hale OP
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I'm all too familiar with these procedures...given I had to build the r90 from the ground up
It's nice to have a mental checklist of things to go through now though!
The petcock has been rebuilt. The carb is an AMAL 30 mm round monoblock which was never really used when the bike was retired. It's simply missing the plastic float needle. I've just been filling the bowl then shutting off the petcock to do test cranks. The air filters is brand new, oiled and the boot is sealed (I can hear it give a nice suck suck suck when I kick it.) Also has fresh lines.
I'm going to wager it's getting some dirty fuel in combination with timing that is reaaaally off. I'll clean the jets, ensure it gets clean fuel at least for the first start and well...I still need to get that timing thing down. I was hoping I could guess good enough to get it cranked and shoot a timing light at the TDC marks I made on the fly wheel. I guess not :(
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Old 06-29-2011, 07:43 AM   #122
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Did some run starting the other night on it just for the hell of it. It sure grunts like it's wanting to start but it's a no go :(
That tells me the timing is way off and the jets possibly are clogged now from the 40 yr old tank gunk that hasn't been fully flushed out.
Thursday night will be the night!

In the mean time, we got some riding in on the alpina (god I love Bultacos!)

Urban Atlanta trails are fun :)
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Old 06-29-2011, 08:15 AM   #123
PSchrauber
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Quote:
Originally Posted by blaine.hale View Post
Did some run starting the other night on it just for the hell of it. It sure grunts like it's wanting to start but it's a no go :(
That tells me the timing is way off and the jets possibly are clogged now from the 40 yr old tank gunk that hasn't been fully flushed out.
Thursday night will be the night!

In the mean time, we got some riding in on the alpina (god I love Bultacos!)

Urban Atlanta trails are fun :)
Great pic, very cool vintage urban trial.

Btw: I would love to see the Alpina in Detail, model and year?
It looks like it is a model of the mid to end 70's?
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Old 06-29-2011, 08:31 AM   #124
blaine.hale OP
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It's a 73 Alpina (250cc version.)
Found it on CL couple of weeks back for an absolute steal price and my brother bought it. Has all the factory stamped bolts and safety wire and metal fenders. Just missing the lights and gauge. It does need a bit of a cleaning and going over but it runs! Haven't really taken any pictures of it yet.
This is the video before we got it tuned a little and idling properly:



My brother just got off the phone with Hugh's and apparently they were shocked and surprised that the Alpina was the first model run of Alpinas...guess thats a good thing
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blaine.hale screwed with this post 06-29-2011 at 01:52 PM
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Old 06-29-2011, 04:35 PM   #125
PSchrauber
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Yep very cool bike and collectable as you already stated, the sound is still more two stroke wise* compared to the "newer" Alpina and Sherpas I'am used to and are playing around, but very pretty.

* When Bultaco switched to the banana and then to the clubfoot rear exhaust the bikes Alpina and Sherpa got this crazy "blo-blop-blop-blo-blop-blop" sound.
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Old 06-29-2011, 08:37 PM   #126
stainlesscycle
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Quote:
Originally Posted by blaine.hale View Post
I still need to get that timing thing down. I was hoping I could guess good enough to get it cranked and shoot a timing light at the TDC marks I made on the fly wheel. I guess not :(
yeah, the timing is so critical on a 2 stroke. without a dial indicator, there is no way to get it even close. once you get the dial indicator in there and see how much difference there is between .090" and .110" you'll see there ain't no guessing... you only have about a .5mm window of where it will run correctly.. everything else is just kicking it for exercise sake.
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Old 06-30-2011, 07:35 AM   #127
blaine.hale OP
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Sounds like once I get my timing precise (tonight) it will crank right up!
Seriously, this is the worst bike I've set timing on haha.
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Old 06-30-2011, 11:28 AM   #128
stainlesscycle
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yeah, it's got the points setup which is a pain. the motoplat is simple...
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Old 06-30-2011, 11:41 AM   #129
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Be sure to mark the case and stator plate when you get the timing right. Also be sure to do a few plug chops at WOT. There's a fine line between a fantastic running 2T and one that's just about to seize.
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Old 06-30-2011, 12:42 PM   #130
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Correct me if I'm wrong but that means run the bike at WOT for a period (I'd say half a mile is all I can spare haha) and kill the engine with still pegged to see the condition of the plug at highest operating temps. This allows proper and precise carb tweaks, I believe?

Been years since I've had to the pleasure of tuning 2 strokes
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Old 06-30-2011, 01:04 PM   #131
stainlesscycle
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that is correct, hold throttle open, hit kill and pull in clutch.. best if done up a very long hill. best to start rich on the main jet. if it blubbers on top and won't rev out it's rich.
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Old 06-30-2011, 03:14 PM   #132
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Be sure to mark the case and stator plate when you get the timing right. Also be sure to do a few plug chops at WOT. There's a fine line between a fantastic running 2T and one that's just about to seize.

Yes, mark the stator plate and the engine case for ease of reassembling in the future. All the Bultaco motors I own have the marks scribed on them already. Once timing is established you never have to do it again, you only have to make sure the point gap is correct. Point gap will radically change timing on these motors.

Dave
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Old 06-30-2011, 05:09 PM   #133
PSchrauber
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I had to look up what you mean with WOT, this means at highest rpm right?

If so I would say don't do that, you have fresh rebuild motor now, this is an old motor design and you have to break in or running in the engine first.

The WOT method is not healthy and does not cover all adjustment possibilities you have. There is an much more easier and not so "abrasing" method to determine the right carburator adjustment.

There are 5 different systems in a carburator that controll the gas flow, each of them is responsible for a different rpm range you see them in the picture below:



The trick is to mark these ranges on your throttlebody, with a duct tape and foil pencil for example.

Befor you start to adjust your carburator be sure that every jet, needle slide, ... is OK the carb is cleaned, you have fresh gas and a new plug installed. The timing of the ignition should be right too. (1)

Then you search a light slopy road that is about 600m long.

Now you get the bikr running until the engine has warmed up to operating temperatur.

Now you ride along the road really gently accelerating in every gear.

If you notice that the engine runs "unclean", abnormal, is unwilling to deliver power then you notice the position of your throttelgrip.

Start again riding up the road and hold the position of your throttlegrip
where the engine did not run right.

If the engine starts to behave like a four stroke or start to "chop" the engine is running to fat.

If the engine is running to lean the rpm of the engine will rise although the throttlegrip position is unchanged. Mostly you also hear a slight knocking. If the engine start doing knocking don't ride further otherwise the piston or cylinder can seize.

Now you can look up the picture where the position where you had the running issue of the gas throttle is combined with the system of gas delivery. Now you can do your changes if necessary.

If you are unsure you can use the plug method, (engine is again already at running temperatur). Now change the plug, (a real fresh one), und ride the road again with the fixed position of your gas throttle where you have the problem. Stop at the end and unscrew the plug to determine how the plug looks.

Saludos coriales

(1) get a mm gauge to adjust your timing, every time you replace your point you mostly have to find the correct timing again anyway.
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Old 06-30-2011, 05:51 PM   #134
stainlesscycle
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yep, you definitely have to break it in. everyone does it differently.

i ride around up to about 1/2 throttle, then decel without pulling in clutch. don't hold steady throttle. just ride around, varying throttle postion (don't wind it out...) - do this for maybe 10-15 minutes. then let engine cool for awhile - maybe 30 minutes - an hour... then do it again. repeat a couple of times, and you should be good to go. each time you can increase throttle position a little bit. the key is to not coast with the clutch pulled. slow down with engine braking. this may be difficult to do if your jetting is way off. having a nice big yard/riding area with some hills in it helps a lot... you want to keep the motor loaded. don't pull the clutch in and zing it. although neato - it's not good for break in.. :)

as pschrauber said marking your throttle grip at 1/4-1/2-3/4 is an excellent way to find where your jetting is off. i use a sharpie on the grip and a mark on the throttle to reference.


wot plug chop only does the main jet. you will find the main jet is the easiest to dial in. i rarely do plug chops. i start way rich on the main, and work down till it stops burbling, then do a plug chop to verify.
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Old 06-30-2011, 05:59 PM   #135
stainlesscycle
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p.s. your alpina sounds slightly lean on the pilot or airscrew.. it's got a little bog when you wack it, then it's slow to return to idle..
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