compression release on A

[2late4me]

Working on an unstyled A that had been rebuilt years ago and never really used since because it had so much compression they couldn't start it by hand. I've had it running recently but still can't crank it by hand. Thinking about boring out the compression release petcocks a little to help with the issue. Has anyone tried this or have a better solution ?

 

[old]

Are you sure the petcock are opening as they should and or not clogged up with carbon etc.???

 

[2late4me]

Had them off, blew them out with air and run a drill bit in them. They have a good stream a of air coming out but have to turn the engine too slow for starting.

 

[Pete in MD]

You said "...but have to turn the engine too slow for starting". If the timing and carb are set up right you don't have to turn the engine "fast". All you need to do is roll the flywheel over TDC on the left hand cylinder.

 

[fixerupper]

If the petcocks are fully open you should be able to get it over TDC without busting a gut. They do come up a little hard but not THAT hard. If the engine is in good tune, as soon as the mag snaps it should fire no matter how slow you turn it over. I have had a two banger start when I was slowly inching it over the top planning on stopping right when the mag clicks to check the static timing.


Are you sure there isn’t something else making the engine stiff? If my 35 A sits for a year without running it is a little stiffer because there is probably a little rust on the bores but once it has run it will turn over easier on a re start.

 

[Mark-Ia]

You should never have to spin a unstyled John Deere to start it. As Pete and Fixerupper stated, the slower you crank, the better they start. You may need to have your mag reworked.

 

[RandyB(MI)]

If the people who re-built it did so with pulling intentions , they may well have put some real high compression pistons in it. If that's the case then , yes , you may need to hollow out the releases some. It won't hurt anything even if that's not the case. Like said tho, on a stock comp ratio US "A" slowly turn with choke to get some mist out releases and it should pull the flywheel right out of your hands.

 

[old]

To me it sounds like the mag impulse is not working as it should. Hand starting one cannot turn an engine over very fast but if the impulse fire as it should it is enough to fire it up

 

[old]

My 1935 B will not start by hand if it has sat for over a year. But if I pull it 10 feet it fires up right away and will then start by hand unless I let it sit a week or more. But on the other hand if it has ever been rebuilt it would have been done by my grand father back in the 40 or 50 or maybe the 60s if ever. As far as I know the head has never been off of it and it does use a lot of oil when running so I use a 60W oil in it when I do run it but it has been 4 plus years since I had it running.

 

[Ron W]

I bleed red. I have well over several dozen red machines. This fall I had a chance to buy a JD B. I always like them. So I brought it home. Fuel tank gummed up, carb plugged, and magneto dead. An old guy once told me that you need to set those hand starts up right and they will work every time. After a little bit, I got spark from the mag but I still ordered a new coil. Went over the mag completely leaving nothing to chance. Long story short I cannot believe how easy it us to start. My 75 yr old father with back issues can nearly turn it over and it starts easy. But you have to know the tricks, how much choke, adjust needle valves depending on temp (difference between 90 deg day and a 20 deg day). Make sure your mag is right, spent thr money.

 

[David G]

I agree with the others, should just have to roll it over TDC to fire, if you need more then there is a different issue.

 

[Tireboy]

You say you have to much compression. The only way you could to much compression to make it hard to turn over is some one put in high compression pistons. There is one other thing to make it hard to turn over is if they shimed the rod bearings a little to tight when they rebuilt it. If you have to much compression and you drill out the pebcoks it will reduce your vacuum to draw in your fuel mixture when starting. I had that happen on a pulling tractor that I used 3/8 ball valves to relieve to much compression.

 

[h3llbilly]

To echo others, you can drill the compression releases some but too much will actually complicate matters more. It's my guess also that someone has put high compression pistons in the tractor for tractor pulling purposes. We did this, along with a planed head, to our 37 A back in the eighties. Without any weights on it, it would skid the rear wheels in high gear while trying to tow start it. You could absolutely not start it by hand.

If it turns over to coming up on compression, you have to really work to get it past the compression stroke, or if it skids the rear wheels in high gear while trying to coast or tow start...it's most likely got high comp pistons. The "force" of the compression release itself should also be heard and noticeable.

You can take a compression test to determine how many pounds of cylinder pressure you're at. If it's in the 200lb range, the original builders were probably looking to get 10:1 compression ratio. It will not hand start!

In my opinion, if you determine its got high compression, there's only a few things you can do. Change the left-hand main, flywheel, and put a starter on it. It will start but you'll be lucky to run reg pump gas or keep it cool to work it. You can change pistons if that's all they've done. It is not uncommon to find offset ground cranks, high comp pistons, and a shaved head. The easiest thing is to have the top of the pistons turned down. Lastly, you can embrace it and enter the addicting, highly expensive world of tractor pulling!

 

[Blue Jay]

Had a good laugh one time, young buck was trying to start an A at a steam and gas show by wipping it over real hard, after about 5 min. of this an old man got up from the stands, hobbled over to the tractor using a cane, the young buck looked at him wondering what he was going to do when the old man stepped up to the fly wheel inched it over the top and the tractor hit and was running, the young buck just stood there and scratched his head, finally said thanks. Bet he won't forget that for a long time.