Good afternoon to all. Friend of mine just picked up a 1970 XLCH 900 Ironhead about 2 weeks ago. Bought it from a kid who's dad passed last year and the bike has been sitting in his garage since 1986. Motor was rebuilt in late 70's or early 80's by Harley because the guy tipped it over at the boat landing carb side down while running. (Not too sure what he was doing with his bike in the water). Kid thinks it needed Primary work, but for 1200 bucks we figured worst case scenario is we part it out. Took it home, pressure washed it, pulled the carb and cleaned it out. Polished the chrome. New battery and some fresh gas and oil (after we took the tank off and cleaned it) and about 1.5 hours of kicking and we got her to run. Seemed like it would not idle down unless you choked it out with your hand over the carb inlet. The front cylinder was also running much hotter than the rear. Tried adjsuting the mixture screws on the carb. No such luck. I figured maybe it was a vacuum leak someplace-either the o-rings on the intake (I assume it is an upgraded carb ((mikuni)) with y-pipe intake that has o-rings between the intake ports and intake manifold with a steel strap clamp around the joints). Have yet to run it again since then.

Question # 2. We also tore the wheels off to get new tubes and tires put on. Got them back from the shop, put them on. Adjusted the brakes and that. Everything seems to work ok there. Clutch seemed tight when we squeeze it. Got it back on the ground, squeeze the clutch, put it in 1st, let the clutch out, And it seems to engage just fine against the motor. Pull the lever back. Does not diesengage the clutch from the motor while in gear. Wondering if this is an adjustment issue, or potentially a bigger problem inside the primary. We do have an original service manual on the bike, but they don't talk. I consider myself pretty mechanically inclined with autos and trucks, but have never worked on motorcycles extensively. (I am currently turning my 07 Honda Shadow Spirit 750 into an old school bobber/chopper cross) Don't mean to get lengthy on you guys, but appreciate any helpful tips.

 

does sound like a intake leak , the clutch problem i have when the bike is cold also, i was told it was too heavy of oil in the primary.

 

I agree sounds like an intake leak. Needs the o-rings in there anyway. Sorry i am not so good on clutch problems. But i would certainly ensure a correct oil [about 1.5 pints] is in the primary, and check the adjustment.

 

First of all, let's talk about the clutch.
The 1970 was the last year Harley used what is called the 'Dry Clutch'. This clutch cannot stand any oil at all on the plates. The clutch hub basket has a bonnet cover with a gasket, and the rear of the hub has oil seals. This is to prevent the clutch from getting any oil on or in it.
If oil gets inside it will ruin the clutch plates and the clutch will slip. Also, the clutch will drag and feel like it is not disengaging, which in affect is just the case.
I am not saying yours is in that condition, but since it sat for so many years it is a possibility. When you first got the engine cranked for the first time, did it not puke oil out on the floor from the metal tube under the timing cover and below the generator?

Next, the carburator......
A Mikuni carb is certainly an aftermarket item. It also is a very, very good carb. It is going to be a 38mm size. You can no longer get any parts or gaskets for this carb as far as I know, so take care of what you have. That includes carb gaskets too.
The Mikuni has a fixed main jet, an adjustable low speed air/fuel mixture screw, and a needle that hangs inside the round slide. This needle has 5 notches on it with a clip inserted into one of the notches.
The notch you want the clip in is the middle one. That is, 3RD from the top, or 3RD from the bottom.



The low speed air/fuel adjustment screw is the small screw located above the float chamber close to the air cleaner backing plate. In the pic above this screw is almost hidden by the nut holding the backing plate on...........pg

 

We gave it a fresh oil change the night we got it running, letting the old oil drain out overnight, so no oil came out of the tube under the generator. The oil we have in it is 20W50 Castrol. That is the only thing that a person we know runs in there older Harleys. Also for the Mikuni carb (Piniongear), How many turns out are your low speed adjustment screws, and your main adjustment screws? I will have to tear it down to see where the clip is at on the needle, but as I recall, it was on the middle notch. I will double check that though. When we did have it running there was no backfiring or popping through the exhaust (even when revving and letting drop down to idle, or what was supposed to be idle). Is the clutch adjustable without pulling the primary cover off?

 

It does not feel like the clutch is "dragging" or Slipping. I cannot tell the difference between when the clutch is in or out when it is in gear. Seems like I get the same amount of resistance from the motor either way. Neutral is fine, but when in gear, no matter if the clutch is in or out. Definatley a solid grab on the engine.

 

Hey piniongear:

Why can't you get parts for a 38mm mikuni anymore? I am thinking about buying a new Sudco mikuni kit for my bike but I hate the K&N air cleaner that comes with it.

What air cleaner are you running on the pic above? I like the fact that it still uses a front bracket to help support the weight of the air filter assy.

Carl

 

Certainly the clutch is adjustable. Your clutch has 6 springs on the outer pressure plate that align the plate. If the springs are not adjusted correctly the plate wobbles and the clutch will drag.
Before you try to check on this be aware that you have to remove the bonnet cover and you will need a bonnet gasket and a primary cover gasket on hand to get it back together.
I suggest you get the bike running smoothly first and then ride the bike to see how the clutch is working.
It will go into first gear with a loud CLUNK! and a jerk. This is normal for an ironhead.
It may even take off down the driveway with you holding in the clutch lever! Again, this is normal for a Sportster that has sat for a long time. Riding the machine will loosen up the clutch. Then you will be able to decide if you need to look into it further.
Hope this helps you some. Start looking at that manual you say you have. Everything (almost) that you need to know is in there......pg

PS: There is no adjustment for the main jet. This is a fixed size jet. You change size by installing another jet. You do not want to do that however as the jet that came in the carb is the correct size for your engine.

 

You may want to lube the clutch cable to ensure it travels freely ..
Also as said it's a dry clutch so they are known to have build up around the perimiter of the plates preventing the plates to disengage

 

Carl.....
I called Sudco in 2000 and talked with their tech person on the phone. I was trying to get a set of carb gaskets.
After a lot of time on the phone he told me that there were no longer parts available for the VMC 38mm carb.
I tried J&P as well and they had nothing. So I gave up. To my knowledge there are no parts. If someone knows different please let me know. The Mikuni is one of the best carbs I have ever had, bar none!
I currently run a Bendix only because I prefer to have the enclosed throttle cable in my handlebars and that is not possible with a Mikuni.
The round air cleaner cover is one I bought from VTwin (a.k.a.Tedd Cycle.....Ah, spit.....)
I went to the parts house and found a Toyoto paper element the fit into the cover. Then I took a piece of aluminum plate and turned a backing plate on the lathe to finish off the air cleaner assembly. So, this is not something that was purchased.
The original air cleaner that came with the Mikuni was a large cast aluminum backing plate and the original 'Ham Can cover' and element was used to provide an air cleaner. While it worked well, I wanted a smaller set up and decided to make my own when I did the major restoration back in 1995-2000.

And yes, before I forget, any carb that you put on a Sportster needs to have the carb brace on it because of the manifold with O rings and the minimal clamping used to hold it in place.
The clamps keep things air tight but do not support the carb. No brace means the carb and manifold are going to move and then that is when the air leaks start to happen.
pg