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Discussion Starter #1
got bike out I built years ago, will not crank over with plugs in! it ran couple years ago, had wet sump problem, just got around to rebuilding oil pump and lapping seat. Now will not turn over with plugs in. Bought new battery and starter not that, pulled carb ( thought stuck float )not that, pulled exhaust (values open and close) not that, took clutch apart, not that. FYI using car battery and jumper cables that I cut ends off and added lugs for good mechanical connection directly to starter and ground directly on motor with toggle switch between starter motor and relay terminal. Works Good With plugs out! Draws a ton of amps with plugs in and turns over maybe once then stops! Thought maybe cylinder wall rust, sprayed with PB Blaster couple times. Any ideas/help would really be appreciated!
 

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When you rebuilt the oil pump could you spin it freely after it was torqued to spec.Could be the pump binding
 

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Sounds like too much compression for the starter.

Confusing that you checked the carb. Is the problem with turning over or firing?
 

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Turns over fine with no plugs (0 compression) and again with PB Blaster would make me think cylinder rust isn't an issue.
Draws a ton of amps with plugs in and turns over maybe once, sounds like an undersized starter since it sounds like you're using enough battery. Did you replace the old starter with a different model new one? Did the old one turn the bike over with plugs out?

I am sure some folks a lot more knowledgeable than me will chime in.
 

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If Tall Terry doesn't chime in, send him a PM. There are others who are also pretty good at trouble shooting odd things, maybe they'll be along.

I'm wondering if your connections are clean and good - especially your ground. It can look okay but then when you take off the nut it can be corroded underneath. You bought a new battery - sometimes they're bad -- you might take it in for a load test just to be sure. Ditto the starter - could it be shorting?

If it's not a connection/electrical related, trying to think what could hold it back. Are you running high CCP and do you have automatic CRs - are they working? You say you had a sumping problem - did you fix it and drain the sump?
 

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Do a compression test,, throttle wide open and plugs out,,, record the numbers,,, add oil to the cylinders record the numbers the post them...
How many amps, exactly are "a ton of amps"? 250, 300, 400? Numbers are important... I've seen a few big street engines take over 300 to engage the starter then 200 to crank.. the minimum battery is around 300 amps nowadays...
What engine are we talking about, what bore and stroke, since you built it you should have this info somewhere. Post this as well please..
A few of us, will give it a good shot at solving..
It it were a mechanical issue plugs out wouldn't matter, unless you were talking about a pan or shovel, made for 3/8 depth plugs. And you have 3/4 depth plugs installed...
Knowledge of what you have, coupled with a good diagnosis is the key to locating an issue with as little wasted time as possible...
 

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Welcome to the forum.

This will be interesting. As usual Terry has some great suggestions. It will be interesting to see what your CCP is. Also as stated above. Do you run mcr/acr?? What starter do you use. You said you built it. Good. What did you start with. A little info would be great. Best of luck to ya.
 

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What's the scooter/starter type?

If it started back when, it should start fine now.

Lots of things that could be going on. Try spinning it over with the spark off. If it'll spin that way, then you prolly need more battery.
 

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If you have not already upgraded your battery cables you should think about it. I think mine are 4g.
 

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4 gauge is good, use the fine wire very flexible cables... you can buy it by the foot, and then solder the terminals on, shrink wrap the connection and just like that ,, perfect cables for about half price.
 

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Discussion Starter #11
117 Stoker Motor

Been working on bike (trouble shooting)! Its a 117 inch stroker motor built by Hot Shot motor works, frame was made by Gamble, Ness transmission, Primo Belt Drive, Bore is 4" Stoke: 4 and 5/8".
Update bought another starter Arrowhead 2.0KW same prolblem.
I really think the problem is motor related. I removed the open belt, the new starter turned the rear tire over in fourth gear with a voltage drop to around 9volts. FYI, plugs out starter voltage drop 5.8 volts, plugs in voltage drops all the way to 1.8 volts I will purchase a compression tester later today and get back to all tomorrow. I have pulled the oil pump also, though maybe bind was there. Built this years ago never really went through it. Life happened. So finding issues here and there been correcting while awaiting the new starter.
I really appreciate the help!
 

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"plugs out starter voltage drop 5.8 volts, plugs in voltage drops all the way to 1.8 volts"

I think this is your problem, that much of a voltage drop is not right. I'll wait for the truly knowledgeable guys to confirm and make suggestions.

Hopefully they can point you in the right direction and keep it inexpensive too.

Post some pics up of the bike...
 

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Discussion Starter #14
Trying to post this again, Terry, compression test, 115 rear no oil, 120 with oil, 117 front no oil , 122 front with oil!
 
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