My 720 Resto

[720inOlyWa]

The engine went back in today, in one huge epic work session. We began just after breakfast and by noon, she was back in again. Jerry had to bug out, so I spent the rest of a very warm Sunday pushing onward. Finally, about 5PM, I was putting things away and filling the radiator before I turned the key. 

 

You can well imagine my scowl and furrowed brow when, upon starting the Fudgecicle again for the first time since the rebuild, she immediately began to emit steam out the tail pipe again. I was exhausted from having done the complete re-assembly in one afternoon, from bare pistons up, so I wasn’t thinking clearly. That’s my excuse, anyway.

 

Gosh, she ran so smooth now, how could there be any coolant leaking into the system? I watched with some chagrin as it got somewhat worse as she warmed up. Gee whiz, it was cool how the rebuilt idler pulley spun so silently now. But what did I do wrong?!? Maybe it was leaking through the intake manifold. Maybe I left something loose. I mulled the possibilities as I jumped in and took a test drive anyway.

 

She just runs up trough the gears like a nice little 720 oughta. What’s not to like? Yet the rear view mirror isn’t lying: I still see steam coming out the damn tail pipe!

 

My shoulders were in no mood to discuss future re-re-re-repair strategies, believe you me. But no matter- it turns out that it would have been an unnecessary conversation. You, being the Ratsunite you are, I’d bet four sentences weren’t finished before you knew the score. It took me until I got home to figure it out. Of course I was seeing the old accumulated shit burning out of the exhaust system. By the time I parked back in my driveway, she was ticking away at the curb with nary a fume visable out the tailpipe.

 

And I drove it. And it was good. 

[Charlie69]

Congrats Man!!!  Happy it all came together for you.

[Lockleaf]

Congrats! I'm glad I'm not the only who after a marathon build has jumped to that terrible conclusion only to realize later I had nothing to worry about. Glad to hear she's purring again.

[720inOlyWa]

There are a few little issues to mop up, but man, it was satisfying to fire her up today and do my daily drive for morning coffee. She just runs along, real sweet like. I am not finished chasing little issues, however. The entire choke mechanism does not seem to be working properly- or working at all. I haven’t tested the continuity of the choke circuit yet, so we are just beginning there. But it is as if the choke is not doing it’s job at all. After reading on the subject, I suspect that maybe I purchased a knock off Weber carb off of ebay, and not the real deal. Now I am not saying that I did, or that the carb is an issue, but I have had my suspicions raised by repeated reports.

 

The one driving issue left to deal with is the same one that I have been chasing since I got her running again: it hits too hard from idle. You press on the throttle and press a little harder, and then it gives way and you are up to 2,200 rpm. Although it feels like it might be the case, it is not due to a sticking cable. From a dead stop, if I tap the throttle before slipping the clutch a little, I can surf the modest bump in rpm to get going and everything goes fine. But you shouldn’t have to do that. You should be able to simply let out on the clutch with minimal throttle pressure and slip away in first, without slipping anything very much. So I still have that to chase down and fix too. But that’s about it.

 

Interesting data  to me, the guy I bought my 4x4 720 from reported the same thing when he installed his Weber. And it has the black choke cover too... (the sign of a knock off, I was told.) Yet another owner, reporting the same issue, suggested that it was a byproduct of the second barrel of the carb kicking in, and that there is nothing you can do about it. While the diagnosis is possibly true, his conclusion cannot be. I drove a 620 with a Weber for years and it was lovely around idle. It didn’t hit too hard at all.

 

I will continue to chase down this balky throttle issue as I get my 4x4 running this week. I have the new head on it, so all it needs is the same marathon reassembly, along with some gremlin chasing, to become a daily driver too.

 

Now I will let you all in on a little secret, something that I have not told to anyone else...  

 

Since the 4x4 is much more likely to become our boat hauling truck later, this little 720 friend is probably going to head over the mountains, to the dry climate of Ellensburg this summer- as a gift to a couple of the most incredible and deserving friends that one could ever hope to have. It will haul nursery stuff, and yard sale finds, antiques, and yard waste, while under the care of a superb mechanic and a friend, indeed. They could really use it.  

 

I really can’t wait to surprise them with the keys, but everything has to be perfect before I give it to them.

[84720FourWheel]

My 32/36 clone is the same way. Doesn't like the low end take off like the Hitachi did. It got a bit better at a lower altitude.

 

Perhaps jetting should be adjusted?

[720inOlyWa]

I am at sea level, so...

There must be something I am missing.

 

On my old Plymouth carbs, there was a little valve built into the butterfly. A small spring kept it closed unless under a certain amount of pressure. But when needed, it lifted open to help break that vacuum seal there and allow a little air to spill through, thereby ‘softening’ the throttle advance. A really clever idea, I thought. It seems like this carb could use it.. 

[Lockleaf]

One thing to check for on your carb is throttle shaft wobble. These throttle plate shafts ride on the carb case and can actually wear the case in weird ways that cause vacuum leaks and throttle binding. The cases are cast with a place to run a bearing on each end of the throttle shaft, but I've only seen full race versions sold with them. You can find them online or go to your local r/c nitro type hobby shop and find a bearing that is 12mm od and 8mm id IIRC.

 

These are the kit I bought.

https://www.pegasusautoracing.com/productdetails.asp?RecID=5949

 

Here's a video explaining the problem and showing the repair.

 

Hopefully that at least gives you a new idea to look in to.

[720inOlyWa]

So ordered.

I mean, come on- what’s not to like? You’re adding bearings!

 

Thanks!

[harlow426@mail.com]

One thing to check for on your carb is throttle shaft wobble. These throttle plate shafts ride on the carb case and can actually wear the case in weird ways that cause vacuum leaks and throttle binding. The cases are cast with a place to run a bearing on each end of the throttle shaft, but I've only seen full race versions sold with them. You can find them online or go to your local r/c nitro type hobby shop and find a bearing that is 12mm od and 8mm id IIRC.

 

These are the kit I bought.

https://www.pegasusautoracing.com/productdetails.asp?RecID=5949

 

Here's a video explaining the problem and showing the repair.

 

Hopefully that at least gives you a new idea to look in to.

 

 

So ordered.

I mean, come on- what’s not to like? You’re adding bearings!

 

Thanks!

Right on....just the info I needed to snuff up a weber that has served me well!! Shaft bores were worn when I got it....THOUSANDS of miles ago. BITCHIN'!!

[harlow426@mail.com]

There are a few little issues to mop up, but man, it was satisfying to fire her up today and do my daily drive for morning coffee. She just runs along, real sweet like. I am not finished chasing little issues, however. The entire choke mechanism does not seem to be working properly- or working at all. I haven’t tested the continuity of the choke circuit yet, so we are just beginning there. But it is as if the choke is not doing it’s job at all. After reading on the subject, I suspect that maybe I purchased a knock off Weber carb off of ebay, and not the real deal. Now I am not saying that I did, or that the carb is an issue, but I have had my suspicions raised by repeated reports.

 

The one driving issue left to deal with is the same one that I have been chasing since I got her running again: it hits too hard from idle. You press on the throttle and press a little harder, and then it gives way and you are up to 2,200 rpm. Although it feels like it might be the case, it is not due to a sticking cable. From a dead stop, if I tap the throttle before slipping the clutch a little, I can surf the modest bump in rpm to get going and everything goes fine. But you shouldn’t have to do that. You should be able to simply let out on the clutch with minimal throttle pressure and slip away in first, without slipping anything very much. So I still have that to chase down and fix too. But that’s about it.

 

Interesting data  to me, the guy I bought my 4x4 720 from reported the same thing when he installed his Weber. And it has the black choke cover too... (the sign of a knock off, I was told.) Yet another owner, reporting the same issue, suggested that it was a byproduct of the second barrel of the carb kicking in, and that there is nothing you can do about it. While the diagnosis is possibly true, his conclusion cannot be. I drove a 620 with a Weber for years and it was lovely around idle. It didn’t hit too hard at all.

 

I will continue to chase down this balky throttle issue as I get my 4x4 running this week. I have the new head on it, so all it needs is the same marathon reassembly, along with some gremlin chasing, to become a daily driver too.

 

Now I will let you all in on a little secret, something that I have not told to anyone else...  

 

Since the 4x4 is much more likely to become our boat hauling truck later, this little 720 friend is probably going to head over the mountains, to the dry climate of Ellensburg this summer- as a gift to a couple of the most incredible and deserving friends that one could ever hope to have. It will haul nursery stuff, and yard sale finds, antiques, and yard waste, while under the care of a superb mechanic and a friend, indeed. They could really use it.  

 

I really can’t wait to surprise them with the keys, but everything has to be perfect before I give it to them.

Payin' it forward! :thumbup:

The world would be a much better place if more people were like U.

You get back what u put in!

[izzo]

I can't see the pictures :rofl:

[hobospyder]

i used to have an issue with my throttle cable sticking after i switched the carb. maybe make sure it's got a straight shot to the linkage on the weber and it's not riding on the walls of the housing?

[Lockleaf]

Harlow, OlyWa, AWESOME. mine was not only vacuum leaking, but the throttle shaft had so much wobble in it that it would bind the secondary throttle actuator. I could not go past 3/4 throttle and I was not using the second barrel at all. For me, those bearings made a huge difference, fixing both problems. Hope they help you guys too.

 

And, like hobo, i have had issues with cable binding due to a bad approach angle for the cable. I ended up building a fully custom cable bracket to get things right.

[Charlie69]

I had trouble with my Weber not returning to idle on my 86 720 KC.  I put a return spring on it and now it will idle as low as I want it.

[720inOlyWa]

I did the dance with throttle return springs and came to the conclusion that I was looking at the problem from the wrong angle. One regular return spring ought to do the trick. If it isn’t returning to the stop position every time you let off the gas, I’d first look to the shaft binding in the throttle body.

 

Those throttle shaft bearings sure make sense to me, especially since the problem vanishes briefly whenever I douche the throttle shaft area- inside and out- with carb and choke cleaner.

 

After checking the head bolts, I re-timed it this morning, re-set the choke after tearing it all down and putting it back together, and then did the throttle shaft soak. And today, it runs just like a brand new truck. Take offs from zero are nice and sweet. It makes me think the throttle shaft bearings, when they get here, will make all the difference. 

 

It’s finally time to haul the load of bullshit I have had in the bed since before this rebuild, to the dump!

[Charlie69]

If you are depending on the little coiled return spring that is on the throttle shaft to return the throttle shaft and the cable to idle it is not enough to push the throttle cable back also  If you look at the design of the throttle pedal and the throttle cable when you let off the pedal the pedal returns but the cable is design to stay in the position until the return spring at the carb pulls it back to the idle position.   When you change out the factory carb to the Weber there is a throttle return spring that is removed. I have not had any success using that spring on the Weber, it is to weak/not long enough.  I have a set of bearings that I will use when the throttle shaft gets sloppy and causes a vacuum leak.

 

This is the throttle return spring I used I only used the smaller diameter spring and installed the bracket under a valve cover bolt.

 

http://www.jegs.com/i/JEGS-Performance-Products/555/15225/10002/-1

[720inOlyWa]

Oh sorry, Charlie. I miscommunicated.

I assumed that we had all been through the same return spring caper. (I probably assumed this because my second 720 showed clear evidence of having gone through the same routine that I did, suggesting a pattern.)  First step, you realize that the spring hanger they give you is in the wrong place and therefore offers little mechanical advantage right where you want it. Second step, you bend the supplied hanger into all kinds of wicked shapes trying to get the spring over center. Third step, this looks horrible, so you shitcan their  return spring hanger altogether and invent your own over center return spring mount.  

 

In my case, I even added a second spring for a while to really get the things to go solidly down to idle every damn time.   But that was missing the point, and probably adding to the throttle  shaft wear as well. The resistance to a smooth and predictable travel is often in the throttle shaft itself, whether it gets shellacked, or it wears the hole from asymetrical loads and binds. Geeze, I hope that makes sense. I really believe the shaft bearings are going to help take care of this problem. Again, thanks harlow!

 

It is getting cold now tonight and the truck has been in the driveway all afternoon. Time to do a cold start test, to see how I did with my choke adjustment... Holy cow, that worked great! It held the warm idle rpms nicely even when it was dead cold!  A little tap on the throttle confirmed that the choke had been doing its work nicely. Yet another small victory.

 

Go Hawks!

 

https://www.youtube.com/watch?v=kYXvO_4SPL4

[Charlie69]

I will take a picture.

 

I buy my Weber kits from Pierce Manifolds and theirs do not have a bracket and spring. 

[720inOlyWa]

I had a couple of hours free to do a 100 mile check up today. I pulled the plugs and they seemed real good and even to me-  clean and tannish electrode, turning to light dusting of charcoal around the base. All are the same, none are being dissolved, gooped up, or burned in any way. Kinda neat to see that. While I was in there, I checked all the manifold bolts and re-torqued the head.  There was a small oil leak at the back of the valve cover that was beginning to seep down the back of the block, so I tossed a new valve cover gasket on there as I backed out of the job and snugged everything real good. I lost a couple of Weber air cleaner clips during this process, by leaning on the air cleaner a little too hard as I did this or that. That miserable fucking air cleaner and I are just about ready to part company in a dramatic way and for good.

[wayno]

I do the same thing all the time, I lean on the air cleaner when I am bending over trying to see something on the back of the block, and that freaking airfilter compresses and the clips fall off, then I have to use a pair of needle nose pliers to straighten out the air filter element so the clips are tight again that hold the top on, it just gets old after smashing it for the 5th time.

I had a couple of hours free to do a 100 mile check up today. I pulled the plugs and they seemed real good and even to me-  clean and tannish electrode, turning to light dusting of charcoal around the base. All are the same, none are being dissolved, gooped up, or burned in any way. Kinda neat to see that. While I was in there, I checked all the manifold bolts and re-torqued the head.  There was a small oil leak at the back of the valve cover that was beginning to seep down the back of the block, so I tossed a new valve cover gasket on there as I backed out of the job and snugged everything real good. I lost a couple of Weber air cleaner clips during this process, by leaning on the air cleaner a little too hard as I did this or that. That miserable fucking air cleaner and I are just about ready to part company in a dramatic way and for good.

[84720FourWheel]

Did you rtv the semi circular plugs? It'll end up leaking again if you don't.

[Charlie69]

For anyone interested I posted my return spring pictures here.

 

http://community.ratsun.net/topic/65049-charlie69s-86-720-king-cab-dd/page-2?do=findComment&comment=1204748

[720inOlyWa]

Really, I am just a little pissed at myself for not getting the stock air filter conversion done by now. When I hear those clips falling off, it just reminds me that I should have finished that project up. Which I will. Now. The sexiest part of a carb is the air cleaner and look what Weber gives you for over $300- a total POS.

 

I though that the bad valve guides were the cause of my hard initial cranking when cold, by leaking oil into the cylinders while it sat.  But it continued after I replaced the head and the guides were new. That means it was gasoline, not oil, that was seeping in there while it sat. So I adjusted the float in the carb yesterday and now, that little issue is gone. Check another one off the list.

 

With the previous head failure condition, it was impossible to get a very good read on the carb setup. Too many other things were wrong, plugs getting fouled, all the rest. Now that the engine has been refreshed, the ‘hard cranking when cold’ culprit could be tracked down and banished. It was in the carb.

 

I have been complaining about it hitting too hard from idle since I got it running, over a year ago. To remedy this, I did everything but the right thing. I replaced throttle cables, tweaked the return spring ad nauseum, on and on. Really, in the end, the problem was that I was running a little lean. A few days ago, as I began to really study my carb in depth, I went through the entire setup instructions again and did it all, beginning with the float bowl adjustment. I think it is pretty close now, though one wonders about a leaner jet package (“cheep. cheep.”)

 

With the carb adjusted more or less correctly, you can grandpa drive this bitch all over the Safeway parking lot and she manages just fine. Acceleration is smooth and sweet.    And finally, I know why.

 

It is a shitty day out today, but those throttle shaft bearings arrived yesterday. If I hadn’t finally nailed the problem of the hard hitting throttle, I’d be out there installing those bearings right now. As it stands, the setup is working so damn good that I don’t really need to mess with it. Maybe I will save them for the 4x4’s carb...

[Lockleaf]

I drilled 2 holes in my Weber lid and replaced two of the air filter base mounting bolts with pieces of all thread. Those stick up about half an inch above the lid and I just put some nuts on there. Eventually I keep thinking I will put on something nice looking, but it works great.

 

[Charlie69]

That is the first Weber I have seen mounted in that direction

 

Here is mine on my 86 720 KC