Thought I would share this incase anyone else out there has the same issue.
I finally got an XR75 this past march from my buddy that was fairly thrashed out. It ran but didnt like too, and one of the past owners had completely hillbill-ified it.
Some of the neat options they had added to it over the years included:
Tractor inner tube rubber for a seat cover, zipped tied down.
A broken light mont in place of the number plate. 75’s don’t have a stator so I’m not sure what was powering it.
Some weird cafe racer styled pipe handle bars. They threw out the bar clamps as well.
Lawn mower muffler welded halfway around the stock pipes down tube.
A masking tape intake boot. Enough said, this what this post is about.
The bike ran like crap with a giant hole in the intake boot covered in masking tape so when Chad came over one day he decided to try and patch it up with some of the rubber from the old seat cover that was replaced. After cutting off a small slice and wrapping it around the old boot with rubber cement and a hose clamp to hold it the bike ran better. It still fouled out plugs like crazy and would randomly spit and sputter all the time. After replacing the jank-tastic handle bars with some off a crf80 one day, I started tossing the little XR around the trails and came off a jump just a little to hard. A funny sounding BWWWAAAAAAAAAHAAAAAAAaaaaaaa… burp.. came from the engine and it costed to a stop. I looked down and the carb was laying on my knee. So here a the fix for 73′-76′ long intake boot, I’m not sure how the 77′-79′ are setup, I think the intake is shorter.
You will need a xr80 or crf80 intake manifold, and if your getting fouled plugs and odd stumbling issues you should also think about getting a new crf80 carb as well. Dont get a used one unless its from a newer bike that looks like it was not trashed and well taken care of. A bad used carb will just cause the same issues your fighting. New carbs can be found for $85 bucks from partspitstop.com, I picked up a used carb off a very clean 04′ crf80 which worked out great. Thanks to xrminiracer.com for suggesting the carb swap.
So heres the old intake that tore in half, no worries though.
The CRF80 intake shares the same bolt pattern as the xr75’s but is much shorter, non-adjustable, and at the wrong angle.
We need the flange off the crf80 intake to replace the rubber flange thats on the 75’s. Place the CRF80’s intake in a vice and using a pair of channel locks twist it until the rubber part shears in half. Now take the carb side of the CRF flange, you don’t need the head side of the intake.
In order to slip a hose around this the rubber will all have to come off. Get a razer blade or a knife and start slicing the rubber vertically so that it will peel off in small chunks. The epoxy they use on it makes this a pain, but it will come off.
Here’s the what you end up with after you have cleaned the rubber off the CRF80 intake so you can slip a chunk of rubber hose over its flange and onto the XR75’s intake. The bore size is the same, and no more leaks!
Installed and ready to go. My 75 started the first kick with the new carb and intake and every miss, stumble, sputter, went away. The bike also doesn’t run rich anymore and has stopped fouling plugs. The rubber hose for the intake slip was a pain to find. I ended up bringing the intake with me to Autozone and walked back to the radiator hose rack untill I found a smaller hose that fit. The flange after the rubber is peeled back on the CRF80 is kind of small but I have not have any problems with the carb coming loose and I have tossed the bike around pretty hard at times. So there ya go, hope that helps.