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RSRBOB, Technician
Category: Motorcycle
Satisfied Customers: 1078
Experience:  Former Factory Service Rep, Dlr Line Tech, Service Manager, General Manager, Store Owner
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2001 Polaris Scrambler 50..... Put a 70cc head on it and ne

Customer Question

2001 Polaris Scrambler 50..... Put a 70cc head on it and ne w Battery, starter, stator, cdi box, rectifier..... Has a hard time cracking over... Battery is a 13.03v and have it on a tendor, if you take the plug out she cranks right over.... Put the plug in and it hardly cranks.... I even tried jumping it off my truck today and and it still wouldn't crank over... Any help???
Submitted: 5 months ago.
Category: Motorcycle
Expert:  RSRBOB replied 5 months ago.
Hi and thank you for your question.The immediate response that comes to mind is the starter does not make enough torque to spin the engine over to start it due to an increase in compression.To be able to assist you further, and to explore possible solutions, I would need to know who makes the 70cc parts that you installed. Also, for clarification, Did you just put the 70cc cylinder head on it or did you put a 70cc piston, cylinder and head on it? Did this come as a kit and if it did, did it give the specs on what its compression ratio is?The one statement you made about connecting your truck to the ATV and not improving upon the cranking speed, along with the fact that it cranks right over with the plug out, leads me to the conclusion that the starter just doesn't make enough torque to crank the engine due to the increased compression.If you could get back to me with that additional information, we can explore options for resolving the issue.ThanksRSRBOB
Customer: replied 5 months ago.
I had bought the kit from Coles cycle.... It is an upgrade kit from 50cc to 70cc....It ran all Easter Day no problem.... It's a Caltric starter from eBay...
Expert:  RSRBOB replied 5 months ago.
Thank you for the additional information.So what you are telling me now is this ran fine after you put it together and for at least one day. Then all of a sudden it will no longer electric start? Odd to say the least. do you have the ability and equipment to do a compression test to see what it is cranking for compression now? If so, did you happen to do a compression test immediately after the kit install? Do they recommend premium gas with the 70cc kit?ThanksRSRBOBPS, if there are any more details about the history of the installation of the 70cc kit, the running and riding, and possibly unexplained engine quitting please share as much detail as possible.
Customer: replied 5 months ago.
Tried to,compression test today and it cranks 5 times and dies out. But it did,go yo to 90psi. That's with the exhaust pipe off and the air filter. Wanted to make sure there weren't any obstructions......took head back off today and everything was fine....
Customer: replied 5 months ago.
what can I do about having too much compression..... Take the 70cc kit off or can I get a heavy duty starter. Already have too much in this thing,,,,
Expert:  RSRBOB replied 5 months ago.
Thanks,What were you looking for when you took the head off?Just to clear the air, any question I ask you, I really need you to answer or it limits my ability to help you reach a speedy solution to your problem. I am sure you are in agreement with me that something must changed between the first time you ran it and presumably the 2nd time. I am really not even sure of that. I am real fuzzy on whether you shut it off after it was running fine, never to electric start again, or if it quit while riding and then wouldn't restart.So here is what I need:1) Does the kit tell you what the projected compression ratio is supposed to be when installed on a Scrambler 50?2.) What city is the Cole's Cycles in that you got the kit from? I was trying to see exactly what you got and several Cole's Cycle came up. Perhaps if you have the part # ***** the kit I can really pin point what parts you installed.3.) How long did it run normally before this problem showed up?4.) Did it quit while riding or did the ATV get shut off normally and would not restart?5.) What were you looking for when you took the head off, and was it just the head or did you take the cylinder off too?6.) Was the ATV running fine before you installed the 70cc kit?7.) Was the kit installed to resolve another problem, like a piston seizure (or anything else) or was it running fine (normal) and you just wanted to increase performance?8.) Did the Caltric starter specify it was HD for the Scrambler 50? I looked on their website and saw no reference to HD or even more applicable, high torque. Heavy duty could refer more to long term durability as opposed to high torque, which is what one would normally associate with an application where the compression ratio has been increased significantly from stock. Perhaps in some of the starters designed for larger ATV's they specify that but I could not find that on the 50cc Scrambler starter.Help me help you by providing those answers and we can move forward from there.ThanksRSRBOB
Expert:  RSRBOB replied 5 months ago.
Just saw your question about taking the 70cc kit off. I am not ready to jump to that conclusion just yet. Mainly because you said it ran fine at least once, and you never mentioned difficulty starting it that time. That leads me to believe the 70cc kit will work, as long as everything is right.RSRBOBPS, there are alternatives to lower the compression and retain the 70cc kit, but to me that is putting a band aid on the real problem, not really fixing the root cause of the problem.I am also really skeptical that any one actually makes a high torque starter for the 50cc Scrambler just because there would not be a demand for them. They may exist, but I suspect they don't.
Customer: replied 5 months ago.
I wasn't able to find a heavy duty one.
Expert:  RSRBOB replied 5 months ago.
OK.What about the answers to the other 8 questions?RSRBOB
Customer: replied 5 months ago.
1. No it it it dot state the compression ratio...
2. No ide where Coles cycle is from....they vpsell on eBay... only ran for a short Tim but it was always hard starting....sometimes I kicked it over...
4.i took the head off to make sure the rings were lined up and there was no internal damage..
5. Yes it was it was blowing smoke the rings were worn...I was looking to get more power for my son....
6.rings were worn and I wanted to pick up,some performance...
7.Caltric did not specify Hd.... I could not find on that was..... That is what was in there for 10 years...
8. I was told on the Polaris forum to get this to,run right with the extra compression, I would have to run a 24 volts starter.....thats what they doe with these little Scrambler......I might just run it with 2 gaskets and order a new set it rings and change it back over to a 50'and sell,it and buy him a bigger bike.
Expert:  RSRBOB replied 5 months ago.
Thank you for the additional information. To get 24v out of 2 12v batteries you have to connect them in series. This seems radical but ok. The 2 head gaskets could help, but one other option to consider is an old trick 2 strokes used to use. Drilling a small hole from the cylinder to the exhaust port. A small hole, about 1/8" in diameter and about 8mm above the top edge of the exhaust port. That way, at low cranking speeds it will blow off a bit of the compression, but at higher RPM's it will be so small and insignificant you will not feel a decrease in performance...Those are about the easiest things to do. Beyond that it would be necessary to hog some material out of your combustion chamber. If it has that much compression, I would also suggest running it on premium gas only. Regular or mid-grade will probably produce detonation and damage your piston.RSRBOB
Customer: replied 5 months ago.
Think I'm going to put a decompression valve....that wold be easier....
Expert:  RSRBOB replied 5 months ago.
Whatever you think is best. Typically those are installed in the cylinder head. Usually the head is drilled and tapped for the mechanism. Hopefully you have room for it with such a small combustion chamber.Btw, just for the record, some of the big 4 manufacturer's use the hole from the cylinder to the exhaust port as a decompression mechanism with no moving parts.Best of luckRSRBOB

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