Topic: Re: High Comp Pistons (Read 2535 times)

OTIS · « **on:** July 16, 2005, 01:04:45 AM »

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Has anyone found a set of high compression pistons that will put about 10:1 compression on a set of stock 103 heads ?

David buy pistons and heads its worth it and it will make you happy.

OTIS

DavidB · « **Reply #1 on:** July 16, 2005, 01:06:07 AM »

Has anyone found a set of high compression pistons that will put about 10:1 compression on a set of stock 103 heads ?

DCFIREMANN · « **Reply #2 on:** July 16, 2005, 01:44:50 AM »

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Has anyone found a set of high compression pistons that will put about 10:1 compression on a set of stock 103 heads ?

Harley has them but you must modify your 103 heads or buy the 103 plus heads from Harley. That will yeild about 10.5 to 1. The pistons can be relieved to lower compression
ratios. But you must modify your exsisting heads for these pistons. I am at work till tomorrow and don't have the part numbers in front of me.

Be Safe

THE DAWG

DCFIREMANN · « **Reply #3 on:** July 16, 2005, 07:15:10 AM »

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David buy pistons and heads its worth it and it will make you happy.

OTIS

Thanks Otis I don't think I could have said it any better. I wasn't going to buy heads and modify the stock ones. After I saw them it was an easy choice.

Be Safe

THE DAWG

DavidB · « **Reply #4 on:** July 16, 2005, 06:18:32 PM »

Dawg

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Thanks Otis I don't think I could have said it any better. I wasn't going to buy heads and modify the stock ones. After I saw them it was an easy choice.

Be Safe

THE DAWG

Dawg,
With the compression increase does the bike have any problems with preignition or detonation ?

DCFIREMANN · « **Reply #5 on:** July 17, 2005, 08:01:23 AM »

David I will let you know in September when I do the changes. I am waiting that long because I am going to do the timken bearing upgrade and the cases will have to be split.

There are a few on here that have done the increase and have reported no problems. You will need the race tuner, power commander or the thunder max and you can change your timing with any of these so I don't think you will have a problem.

Be Safe

THE DAWG

SHRADER · « **Reply #6 on:** July 17, 2005, 12:31:26 PM »

If you want serious power, over 110HP and TQ, scrap the stock heads. You can buy a set of HTCC CNC Ported or 103 plus heads for a little over $1200. The beauty is that there are forged pistons available from HD and there is no waiting, just bolt them in.

By the time someone works on your stock heads to make them as good as either of these heads you will have spent several hundred dollars and been without a bike for a long period of time. Look at the SEEG Top Dog thread for a list of parts used in my SEEG. 113HP and 115TQ with stock throttle body. All with everyday driveability.

IMHO this is one case where it really makes sense to "spend" more money cause the "value" is there. If I had to do it again I'd probably buy the 103 plus heads. They are a little less expensive than the ported heads, and the boys at SE claim that their flow is very comparable to the HTCC ported heads.

REGARDS
SHRADER

DavidB · « **Reply #7 on:** July 18, 2005, 09:09:45 AM »

A HD shop in Wisconson is using aftermarket pistons on the 103`s that bump the compression to 10:1 . The mechanic working on my bike ordered a set from them and will install them in my bike after doing a little head work on it. ( Opening up the exaust ports and replacing the valves with high flow valvesand unshrouding the seats). I`ll post the results after its dyno tuned.

the O`Fender · « **Reply #8 on:** July 18, 2005, 10:23:48 AM »

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David I will let you know in September when I do the changes. I am waiting that long because I am going to do the timken bearing upgrade and the cases will have to be split.

There are a few on here that have done the increase and have reported no problems. You will need the race tuner, power commander or the thunder max and you can change your timing with any of these so I don't think you will have a problem.

Be Safe

THE DAWG

DCFireman has someone convinced you that the stock bearings are going to fail? I have heard the talk about how the timken bearings being superior but the many people that I have spoken with believe that the 4-3/8" stroke was not enough to cause the roller bearings to fail. I don't know what you are buildin', a drag bike or a tourin' bike?

DavidB harley makes a 10.25 to 1 CAST set of piston that are very inexpensive ($130). At that ratio you won't need compression releases.

DCFIREMANN · « **Reply #9 on:** July 18, 2005, 07:11:27 PM »

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DCFireman has someone convinced you that the stock bearings are going to fail? I have heard the talk about how the timken bearings being superior but the many people that I have spoken with believe that the 4-3/8" stroke was not enough to cause the roller bearings to fail. I don't know what you are buildin', a drag bike or a tourin' bike?

DavidB harley makes a 10.25 to 1 CAST set of piston that are very inexpensive ($130). At that ratio you won't need compression releases.

I have actually seen quite a few that have failed. The roller is good to 100 ft lbs. The last thing I want to do is replace my cases with my own money. Some people at the Moco have even admitted there is a problem. It is a touring bike a sport touring bike. I will not go into the whole motor setup as of yet but it is all ready exceeding 100 ft lbs. It is cheap insurance for thr 350.00 it is going to cost to have it done.

Be Safe

THE DAWG

DCFIREMANN · « **Reply #10 on:** July 18, 2005, 07:12:44 PM »

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A HD shop in Wisconson is using aftermarket pistons on the 103`s that bump the compression to 10:1 . The mechanic working on my bike ordered a set from them and will install them in my bike after doing a little head work on it. ( Opening up the exaust ports and replacing the valves with high flow valvesand unshrouding the seats). I`ll post the results after its dyno tuned.

David which aftermarket company is making the pistons?

Be safe

THE DAWG

DavidB · « **Reply #11 on:** July 19, 2005, 07:14:17 AM »

I dont know who is making them but I`ll know more after they get here. Im gonna be heading out to Washington State to pick up my Ultra thursday and will be home in a couple of weeks. I`ll try and find out who the manufacturer is.

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David which aftermarket company is making the pistons?

Be safe

THE DAWG

Author Topic: Re: High Comp Pistons (Read 2535 times)