MX175 Barn Find

[Weldangrind]

My son and I picked up a '78 MX175 barn find (pics later), and we have a question about oil injectors.

The bike hasn't run yet, so we're not into investing any cash at this time. The most we're springing for is oil, fuel and maybe a Chinese air filter, K&N style. On this model, the oil injector is located behind a cover on the right side of the engine. The pump drives off of a worm gear that is directly connected to the crankshaft. Oil flows out of the tank, into the injector and then an appropriate amount is pumped to the carb, based on throttle input.

The problem is that the entire pump assembly has been wet for a number of years, and it is completely rusted. We took the pump apart, and the gasket has disintegrated and a large spring inside is soon to follow.

We'd like to run without the injector and use premix. As far as I can tell, if we remove the pump and hoses, remove the oil tank, plug the port on the carb that was the oil delivery point, remove the pump cable and run around 40:1 premix, the bike should live. Any thoughts?

[fishman10]

All would work, I might start with 32/1 mix and see how it reacts, yamaha always ran their injector units heavier than needed , probably to be on the safe side. My 1980 mx smoked alot with the stock injector setup.

[VinceDrake]

Something I know something about! Yay!

I had Yamaha Rd series bikes, and did exactly that on all of them-- But yes a 32:1 is a better mix, especially for a barn find...

That being said, the RD350's the oil injector pump also acted as a crank seal... So the Injector housing had to stay in place-- Usually gutted and siliconed up, to keep the vac leaks away...

--Vince

[Weldangrind]

Thanks for the input guys. I recently got rid of a PE175 that required premix, and the manual called for 20:1; it killed mosquitoes for miles. I tried 32:1 and then 40:1 before it was tolerable. I still have a full jerry can of 40:1, so I figured I'd try it.

If you guys think that 32:1 would be safer, I'll dump some more oil in.

BTW, the worm gear that drives the pump seems to have a seal, but we'll check more closely before we fire it up.

[AZ200cc]

40:1 seems like it would be fine, Modern oils are better than the oil time stuff. But I am not an expert on 2 smokes.

[suprf1y]

That's exactly what I was going to say. Modern oils are so good.

I recently found a quality 2 stroke oil that can't be beat for value. Castrol Grand prix 2 stroke, It's for competition bikes, and $4/liter at Partsource.
I'll bought it for my KDX, but probably try it in the RM when my supply of castor oil runs out.

[Cal25]

My brother had a 1975 enduro 100 that he bought new. I dont remember the details but he did have an injectiom pump go bad. I remember the Yamaha mechanic say it was very very rare for that to happen. He just ran pre-mix in the bike from that point forward. Its a little more trouble for a bike ridden on the street, but for trail riding it is no problem using pre-mix.

[Reveeen]

Pre-mix is denser than plain old gasoline. What this means to you is: it is very likely you will have to increase the size of the main jet in the carb, otherwise in WOT (wide open throttle) situations it will run leaner than intended.

SO: WATCH THE PLUG!

[Weldangrind]

Thanks for the additional comments, guys. 8)

I'll be watching the plug closely. I figured that there might be a jet difference because the oil was injected at the carb exit, meaning only raw fuel flowed through the bowl and jets.

[Jim]

I'm sorry but I think it's time to demand pictures :wink:

[Weldangrind]

I'm sorry but I think it's time to demand pictures :wink:

Of course you're right Jim. :D

The seat needs foam and a cover, but at least the base is plastic. One side cover is missing, but I would struggle to even care about that.

http://i158.photobucket.com/albums/t109/Weldangrind/MX175Right.jpg (http://s158.photobucket.com/albums/t109/Weldangrind/?action=view&current=MX175Right.jpg)

There's a little dent in the tank, but it's not bad.

http://i158.photobucket.com/albums/t109/Weldangrind/MX175Left.jpg (http://s158.photobucket.com/albums/t109/Weldangrind/?action=view&current=MX175Left.jpg)

Here's the nasty oil pump after we sprayed Castrol Super Clean on it. It actually freed up a little, but I don't trust it.

http://i158.photobucket.com/albums/t109/Weldangrind/MX175OilPump.jpg (http://s158.photobucket.com/albums/t109/Weldangrind/?action=view&current=MX175OilPump.jpg)

We've got some work to do to free up the brakes and clutch lever. Maybe it'll even start this weekend. :D

[Jim]

Looks good, good luck with it this weekend :)

[AZ200cc]

Maybe a good soak in some Seafoam? Lubes and cleans....Never tried before but could be a cure.

[Weldangrind]

It lives!

We let the tank soak for a week with some rust and scale remover, and I added a handful of stainless screws to act as an abrasive; it did a remarkable job of removing the rust. The original filter and reserve assembly is shot, so we'll just have to keep an eye on the fuel level. An inline filter is cheaper.

I actually had a new spark plug that was exactly the right type. This is gettin' scary.

I cleaned the carb and did a hillbilly mod on the air cleaner, which means I used TurboT's old Beast air cleaner and some ABS pipe. It fits well enough.

http://i158.photobucket.com/albums/t109/Weldangrind/BeastAirCleaner.jpg (http://s158.photobucket.com/albums/t109/Weldangrind/?action=view¤t=BeastAirCleaner.jpg)

I swapped the broken front brake cable for an old XR cable I had laying around. The housing was too short and the cable was too long, so I repositioned the brake arm on the drum until it worked. It grabs hard. The next order of business will be to free up the rear brake; it's rusted solid right now.

I took the seat cover and foam off of an old XR200 seat pan and cobbled it onto the MX175 pan. After a little more trimming, it might even be presentable.

I didn't have another 428 chain that was long enough, so after son of Weldangrind wire brushed the original chain, it got a bath in solvent. It was then blown off with the compressor and given a good coat of Maxima Chain Wax. It seems happy enough.

The pretzled handlebars were replaced with donor XR200 bars. It looks like somebody had a horrible incident with the original bars. 8O

On with the show. Here's the second start-up. I didn't have the camera ready the first time. It starts really easily, and kills mosquitoes for blocks. :D

http://i158.photobucket.com/albums/t109/Weldangrind/th_ItLives.jpg (http://s158.photobucket.com/albums/t109/Weldangrind/?action=view&current=ItLives.mp4)

Here's son of Weldangrind on the maiden voyage. He's taking it easy, because the clutch doesn't work yet, it only has a front brake, and we had to push start it.

http://i158.photobucket.com/albums/t109/Weldangrind/th_FirstRide.jpg (http://s158.photobucket.com/albums/t109/Weldangrind/?action=view&current=FirstRide.mp4)

I think I've since figured out the clutch. After the rear brake is functional, we've got a fun little buddy bike for virtually nothing. :D

[Jim]

Cool, glad to see you've got it going :)

[Cal25]

Good job! The smile on your son's face in the first video sums it up well.

[AZ200cc]

It actually sounds pretty good....Amazing how it held up.

[fishman10]

I had one of those I used to race in the woodsman class at the local motocross track.The woodsmen class was for enduro / hare scramble bikes like the I-T'S ,husky's,Can- ams and such,so I was like a minnow in the ocean,but it was all I had and it was fun even got a 7th once.

[TurboT]

That air filter is going to cost you. High quality parts like that don't come cheap! 8)

[Weldangrind]

Ok, time for some updates.

We managed to free up the rear brake, sand out the drum and lube the cable; it works great. We had a new chain in the box, so we installed it, along with a new 12 tooth front sprocket (down from 14), and a 50 tooth TW200 rear sprocket I had laying around (up from 49). Third gear wheelies are no problem.

We recovered the plastic seat pan with an old XR200 foam and cover we had in the shed, and it looks ok. We installed two new tubes and two decent used tires and took it out for a shakedown run. The kicker kept slipping on the shaft, so we cut a small bit of material out of the clamp to allow it to grab tighter.

We've since cleaned the spark arrestor and repacked it with the same Lexx four stroke stuff that Mizke and Spud used, because that's what we had in the shop.

The bike is now close to presentable, so we don't mind spending a little cash and some elbow grease on it. I picked up a Uni filter that was originally designed for a Kawasaki KLX140L (2008-2010), and it fits rather well. I lubed it with a little Maxima Filter Oil, and it's ready for the trail.

With Reveen's advice in mind, I drilled out the main jet to 0.040" (1.016mm) with my #60 drill bit; not sure what it was originally, because my bits don't go that small.

I cobbled an old Honda throttle tube into the Yamaha housing and removed the original injector cable. The throttle now snaps closed as it should.

Here's the filter cage:

http://i158.photobucket.com/albums/t109/Weldangrind/AirFilterCage.jpg (http://s158.photobucket.com/albums/t109/Weldangrind/?action=view¤t=AirFilterCage.jpg)

Here's the filter installed on it:

http://i158.photobucket.com/albums/t109/Weldangrind/CageinUni.jpg (http://s158.photobucket.com/albums/t109/Weldangrind/?action=view¤t=CageinUni.jpg)

Here it is installed:

http://i158.photobucket.com/albums/t109/Weldangrind/UnionMX175.jpg (http://s158.photobucket.com/albums/t109/Weldangrind/?action=view¤t=UnionMX175.jpg)

Not bad for $20.95. I treated it to the good stuff:

http://i158.photobucket.com/albums/t109/Weldangrind/GoodStuff.jpg (http://s158.photobucket.com/albums/t109/Weldangrind/?action=view¤t=GoodStuff.jpg)

The bike is a really capable old girl. Son of Weldangrind doesn't mind riding it at all while we finish his XR.

[Weldangrind]

We traded the MX175 a few months ago for an old XL250S, and I stumbled upon the old MX175 on CL:

1979 YAMAHA MX175 LOWBALLS PREFFERED - $400 (http://vancouver.en.craigslist.ca/van/mcy/2385160709.html)

He actually has the stones to ask $400 for an old bike with a blown trans. :roll:

[FastDoc]

Sounds like a good trade, Weld! :D

[Weldangrind]

It really was for us. :D

Our Provincial insurance company will grant me the title of the bike once I have it inspected. It will cost about $100 for the process, but it'll be worth it. I'm trying to decide which way to wire it at the present.

Notice how the guy in the CL ad says the bike is immaculate. :roll:

[SpudRider]

We traded the MX175 a few months ago for an old XL250S...
Congratulations on the good trade! :) Please start a new thread on the XL250S, Weld!

Spud :)

[Weldangrind]

I will, but I want the thread to be coherent. I have a few details to work out first, then I'll start a thread.

[2LZ]

Nice find! :D

[SpudRider]

I will, but I want the thread to be coherent. I have a few details to work out first, then I'll start a thread.
Thank you, Weld. Your threads are always superbly coherent; I look forward to your post! :D

Spud :)