74 Honda XL 350 - The Turd

deviant said:
Looking at that last pic, you need to put the rim up on something. The hub should be centered, or have it's proper offset.
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That's the issue I'm having. I generally lace all the inners first, both sides. In this case, everything lines up until that point. When I start installing the outers, they begin to pull the rim too far to that particular side, so that when I start lacing the last set of outers, it's way off.

If i pick the rim straight up as it is, the angle of the spokes don't change, it looks the same as in the pic even when rim is blocked up. ???
 
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I bought that case and an idler gear from the same seller for $9 shipped, it's for a 250 so I will check it out to see if it's the same.

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Tune-A-Fish said:
I bought that case and an idler gear from the same seller for $9 shipped, it's for a 250 so I will check it out to see if it's the same.

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Cool let me know if you don't need.


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This is as far as I got. Based on my photos and knowledge of lacing wheels, the configuration of the spokes should be correct. I had to bend the outers into place and tap them with a rubber mallet to get them to seat.
Old:
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New:
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Here's where I'm at now....
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...but what the f**k? The spokes all the way around appear to be about 1cm too long. Been a long day I could just be botching this job at this point.

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Had to start jumping around now that I'm waiting on the rear wheel. Carb cleaned and reassembled, all new rubber and a new float valve and seat. Not sure where the needle was set so I went right in the middle and see how it runs.

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One thing I noticed, and it's gotten better since cleaned, but the choke butterfly doesn't close all the way. It hangs up on the carb body walls on the left and right side.

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Oh well, chunk it in the trash and get an FCR from an RMZ 250. Just a casualty of war, man. In 78, Keihin started making a single pumper version of the PD carb for their dirt bikes and dual sports. It's basically the #2 carb on a CB750. Just an FYI ;)

If you do keep this'n, pull that cover off the diaphragm on the side and plug the hole up. It's an air cutoff, whose sole purpose is to reduce afterburn. It has zero effect on performance and is just another piece to maintain.
 
You mean the air-cut valve? I'd be interested in swapping out carbs maybe but I'll give this one a shot first, mess with that choke plate if it's a hard start.

Boring stuff today, fixed the kickstand, bead blasted some stuff, got 1/2 controls rebuilt. Mostly trying to make some room on the floor/bench by getting rid of some little easy.



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And that project reminded me why I hate flux core welding, being all lazy and not switching out the wire, ha.


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Yeah, Honda put out a race tech bulletin in the 80s about cutting off the air cut valve. It has no performance benefit, good or bad, except when it gets a hole. Then you have a vacuum leak. It's such an active diaphragm that it's prone to failure. The repops are not well made and tend to fold, and a fold becomes a hole.
 
deviant said:
Yeah, Honda put out a race tech bulletin in the 80s about cutting off the air cut valve. It has no performance benefit, good or bad, except when it gets a hole. Then you have a vacuum leak. It's such an active diaphragm that it's prone to failure. The repops are not well made and tend to fold, and a fold becomes a hole.
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Interesting. The manual states it's purpose is to "prevent backfiring upon rapid deceleration." The diaphragm wasn't in the best of shape when I reinstalled. I think I'll just stick a bolt in the fuel line attached to it and call it a day, that should do the trick eh?


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No fuel line going there. It's all air. Backfiring is exactly why they started using them. It's not bad backfiring at all, just emissions shit. The race tech bulletin calls for a ball bearing in the hole, but a piece of rubber works just as well, if not better. All the info is here... http://www.motorcycleproject.com/text/aircut_valve_more.html and here... http://www.motorcycleproject.com/text/keihin_idle_circuits_white_paper.swf

I absolutely love the PD carbs. Once you get passed the hell it can be to clean them, their performance is great especially with the accelerator pump. Thumpers really like that extra juice to get going. On my '73 250 motor, I'm running a pumper PD carb from an '81 250r. Otherwise, seriously look at an FCR. A lot of 2000s 2 stroke come with them, so they show up on eBay for pretty cheap. One for an RMZ 250 is the perfect carb for an XL350 motor. Mostly, you'll have to take the TPS crap off and add an idler screw, but no biggie. I'll take that to get an FCR for $100 any day.

Here's a bit on how to install and FCR on an old DR. http://www.mxrob.com/FCR_Install.htm
 

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Sweet...FCR seems like a good bang for your buck mod for down the road. Bookmarking that page. As for the air cut valve, I have some 3/16 line running from it just for looks basically. I was saying to plug the end of that to restrict all airflow to the air cut valve, but from your photo there and there article it seems that plugging one of the two small openings is the best way to workaround the valve, so the diaphragm itself still operates.
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Diaphragm doesn't operate when you plug that hole. It acts on vacuum, so in a way it's similar to the diaphragm on a cv carb just serves a different function. When you do the mod, you can remove the diaphragm altogether but as the article points out it will act as a seal so you might as well keep it in there.
 
What I'm wondering is if I can cut off airflow completely to the valve by essentially blocking the brass nipple that feeds the vacuum to the valve? Or do I need to just block one of the two holes inside the valve. It's tough to tell what's going on in that photo you posted, there's not much context.

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It looks like the 'mod' involves plugging that lower hole. But there is one up top as well that feeds directly into the intake end of the carb bore.
 
So I got the 1975 XL250 clutch cover and was elated that it has been upgraded with a needle bearing and seal. The whole cover is very nice but the chain wadded up and took a chunk... The good thing is the chunk is intact an I can weld it back. The idler gear is also a match, I need to check runout but it seems the same just some speed holes.
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