MX175 Barn Find

Weldangrind · 05-31-2010, 02:50 PM

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 · 05-31-2010, 06:36 PM

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 · 05-31-2010, 07:26 PM

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 · 06-01-2010, 12:42 AM

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 · 06-01-2010, 02:52 AM

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 · 06-01-2010, 08:28 AM

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 · 06-01-2010, 10:10 AM

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 · 06-01-2010, 01:35 PM

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 · 06-02-2010, 01:12 AM

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 · 06-02-2010, 01:20 AM

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

Weldangrind · 06-02-2010, 01:56 AM

Quote:

Originally Posted by Jim

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

Of course you're right Jim.

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.

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

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.

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

Jim · 06-02-2010, 01:59 AM

Looks good, good luck with it this weekend

AZ200cc · 06-02-2010, 02:39 AM

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

Weldangrind · 06-07-2010, 02:36 AM

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.

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.

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.

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.

Jim · 06-07-2010, 02:45 AM

Cool, glad to see you've got it going

05-31-2010, 02:50 PM	#1
Weldangrind Join Date: Mar 2009 Location: Sardis, BC, Canada Posts: 25,977	MX175 Barn Find 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? __________________ Weldangrind "I figure I'm well-prepared for coping with a bike that comes from the factory with unresolved issues and that rewards the self-reliant owner." - Buccaneer
	0

05-31-2010, 06:36 PM	#2
fishman10 Join Date: Sep 2008 Location: central PA Posts: 770	premix 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. __________________ 2015 zongshen rx3,,(Sold),,,2016 bashan storm,,2005 Harley ultra classic.
	0

05-31-2010, 07:26 PM	#3
VinceDrake Join Date: Nov 2007 Location: Southern Saskatchewan Posts: 491	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 __________________ "Sometimes it is better to say nothing, and let people think you're an idiot, than to open your mouth and prove it."
	0

06-01-2010, 12:42 AM	#4
Weldangrind Join Date: Mar 2009 Location: Sardis, BC, Canada Posts: 25,977	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. __________________ Weldangrind "I figure I'm well-prepared for coping with a bike that comes from the factory with unresolved issues and that rewards the self-reliant owner." - Buccaneer
	0

06-01-2010, 02:52 AM	#5
AZ200cc Join Date: Apr 2007 Location: Show Low Arizona Posts: 2,889	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. __________________ <br />2001 Suzuki DR200SE<br />1997 Suzuki RM250 YIKES<br />1995 Yamaha Breeze 125 daughters<br />1991 Honda XR80r Restored<br />maybe a 2003 Yamaha TTR90
	0

06-01-2010, 08:28 AM	#6
suprf1y Join Date: Oct 2007 Location: SW Ontario Posts: 408	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.
	0

06-01-2010, 10:10 AM	#7
Cal25 Join Date: Feb 2008 Location: Terrell and Grapevine Tx. Posts: 1,585	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.
	0

06-01-2010, 01:35 PM	#8
Reveeen Join Date: Jun 2009 Location: orbital platform Posts: 741	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!
	0

06-02-2010, 01:12 AM	#9
Weldangrind Join Date: Mar 2009 Location: Sardis, BC, Canada Posts: 25,977	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. __________________ Weldangrind "I figure I'm well-prepared for coping with a bike that comes from the factory with unresolved issues and that rewards the self-reliant owner." - Buccaneer
	0

06-02-2010, 01:20 AM	#10
Jim Join Date: Mar 2007 Location: Abbotsford, BC, Canada Posts: 4,880	I'm sorry but I think it's time to demand pictures :wink: __________________ "Be excellent to each other" "We are all human. Let's start to prove it!"
	0

06-02-2010, 01:59 AM	#12
Jim Join Date: Mar 2007 Location: Abbotsford, BC, Canada Posts: 4,880	Looks good, good luck with it this weekend __________________ "Be excellent to each other" "We are all human. Let's start to prove it!"
	0

06-02-2010, 02:39 AM	#13
AZ200cc Join Date: Apr 2007 Location: Show Low Arizona Posts: 2,889	Maybe a good soak in some Seafoam? Lubes and cleans....Never tried before but could be a cure. __________________ <br />2001 Suzuki DR200SE<br />1997 Suzuki RM250 YIKES<br />1995 Yamaha Breeze 125 daughters<br />1991 Honda XR80r Restored<br />maybe a 2003 Yamaha TTR90
	0

06-07-2010, 02:36 AM	#14
Weldangrind Join Date: Mar 2009 Location: Sardis, BC, Canada Posts: 25,977	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. 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. 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. 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. __________________ Weldangrind "I figure I'm well-prepared for coping with a bike that comes from the factory with unresolved issues and that rewards the self-reliant owner." - Buccaneer
	0

06-07-2010, 02:45 AM	#15
Jim Join Date: Mar 2007 Location: Abbotsford, BC, Canada Posts: 4,880	Cool, glad to see you've got it going __________________ "Be excellent to each other" "We are all human. Let's start to prove it!"
	0