Box Stock

Changing from purple plate to open?

J

jacobsdad

Member
My daughter was supposed to be gone this summer studying overseas but when that fell through she wanted to go racing. So I pulled the purple restrictor out of my sons clone and put it on her kart to run open. It started the season good but has been losing speed. Last week it died on every yellow flag. I changed the coil, valve springs and will change fuel pump (the pump was seeping a little gas). It is still pumping good volume but had a very small leak.
I set the 10.8 valve springs at .002 intake and .003 exhaust. Coil is set at .80. It still isn’t running right.
So, for a clone motor on a 1/8 mile high banked track what jets should I be running? It has the newer ARC flywheel I believe is 32 degrees advanced. Should I run it at 32 or bump up higher? Also is my valve lash about right?
I checked the main jet in the carb but can’t find anything stamped on it. Finally I don’t know what to consider the exhaust pipe. I don’t know if it is small or large, I’m not too experienced with the clone engines.
 
I can tell you the plate carb and unrestricted carbs do have metering differences to optimize each so I probably would swap that out. It def would need jet pulled out of it if your going to reuse it. And I used 36 degrees of timing on mine. ARC 32 wheel and I believe a 5 key got me close. I’m not saying you can’t just pull the plate and run it cause it will run ok like that but it’s not optimal for your situation. Carb may also just need a good cleaning....
 
If the pipe has a screw in muffler that’s a small weenie pipe they call them. The adult unrestricted pipes are full length 2 or 3 stage and take the big 1 5/16 RLV muffler
 
i Knew it wouldn’t be right when we swapped engines but figured it would get her to the track until we had time to change things or get something different for her. The engine has about 8 or 10 nights on it after a rebuild. It was bored a little bit and had some head work done.
I took the carb off and cleaned it out good but it still isn’t running quite right. When starting once in a while it will kick the rope back hard, and sometimes it will backfire through the carb kicking a puff of black smoke out the carb.
I do have 2 new carbs here, but I cNt get it to run on either. One came with an engine I got for another kid the other I think I ordered a few years ago for my son to run restricted. Both have never been raced.
Suggestions on which jet to start with? Also I have a 4 degree timing key here somewhere, would you use that one or get a 5 degree key?
Today I’m going to get the degree wheel out to see where it is set now.
The muffler is the clamp on style.
 
For me that's too much lash .
It does sound like the timing has slipped .
Though that could be the excessive lash.
I've heard you could pull the flywheel nut and see if the keyways are aligned .
Ok course that would only work with a stock key .
Degree wheel is best .
 
I’m sorry, the key I have is a 6 degree. I ordered a 4, my receipt says 4 but the tag on the key I received says 6. Not worth sending back so I put it in my parts box.
 
I’m pretty sure there is no key in it now.
I thought the rockers felt a little loose at .002 and .003 but the original paper I got with the engine when I got it new showed .002 on the spec sheet. I tried spinning the push rods until I had just slight resistance but my fat Chewbacca fingers don’t fit in there to spin them well.
 
Unfortunately I don’t have a 4 like I thought. I have a stock key and a 6 degree key.
I need to see where it is timed now So I know what I’m dealing with.
 
flattop1 said:
For me that's too much lash .
It does sound like the timing has slipped .
Though that could be the excessive lash.
I've heard you could pull the flywheel nut and see if the keyways are aligned .
Ok course that would only work with a stock key .
Degree wheel is best .
Click to expand...
When you say the lash is too much do you mean too big of a gap or too tight?
 
My apologies for posting so often back to back.
I checked timing with a degree wheel. Used a timing light to find where the coil is firing, it is dead on the timing mark. Set the piston to TDC compression stroke. I don’t have a dial indicator so I used a wooden dowel and rotated engine to TDC by feel. Set degree wheel to 0, then rotated until the timing mark lined up with the right side of the coil. In other words set the flywheel to where the timing light showed it was firing.
The degree wheel showed the timing is at 32 degrees. I suspect it slipped because if memory is correct it was set at 38 with the restrictor in.
 
Too much.
That method will only get you within 5 degrees or so.
You need to fab up a dead stop from an old spark plug or anti fouling adapter
Alternatively you could use the dowel find where you think tdc is mark it add 1/4 inch up from there use that mark as your dead stop point . then reset degree wheel using the prescribed method .
 
Its always going g to fire off the same spot on the flywheel . Where the crank is is what changes the timing.
 
I got you. Thanks for the infornation. I reset the valves a little tighter and backed the coil gap down to .65. That made a lot of difference. I have to go to work so won’t be back to working on it until Tuesday night. Next is the carb jets. I still feel like it is running too rich. This is just going by the spark plug and the amount of smoke and fumes it is kicking out in the shop.
And I don’t think I posted but we are running on gas not alcohol.
 
Back the valves off a bit of it’s kicking back. Plate motors are overly rich to compensate for the plate. Take 2 jet sizes out of it to start or just get you an unrestricted carb
 
I’m not sure what jets are in it now, I can’t find any markings on them. I haven’t reset the timing yet either, I don’t have the proper tool for removing the flywheel. I worked at it for a while but don’t want to break anything.
 
You say it has good volume but a small leak!!! The smallest of any leak will get worst. Where was the leak?. Also, if the engine was built correctly, the head will work but not best for unrestricted. If you say it ran decent at first and went down hill from there, I would be investigating that "small" leak
 
We were running it in the shop and noticed the pump was wet between the layers. Dried it off and ran it again, it got wet again. Let it sit for a while and ran it again it stayed dry after that, but the pumps are cheap enough we replaced it.
I might have figured out the running problem for now. I did a closer inspection of the O-ring on the low jet, it was deformed and cracked.
We will see what happens Friday night. I’m hoping this engine will keep her in the top 4 for a few more weeks, hopefully then we will replace it or have it rebuilt.
 
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