hirth 300 piston issues

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matt collins
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hirth 300 piston issues

Post by matt collins » Tue Mar 11, 2008 12:01 pm

Ok people have been asking about the difference between 2 and 3 ring pistons on the hirth 300. They should interchange with no issues. Heres what to look for. THe rings are pinned in place so they don't rotate. This is so the gap wont end up in an open port and break the ring ends. As long as the pins are pointing to a solid part of the cylinder, they will interchange. The two ring set up on later 300 engines was a running change. Most early 2 strokes had 3 rings, but as time went on, engineers realized that 2 or 1 ring gave enough compression and allowed a higher RPM. If you look at cylinders from early and late 300s, you will notice thay are pretty much the same. Wiseco pistons have a 2 ring set up as well. Some of these wiseco slugs are still around. The other option is to send out the jug and have it sleeved to take it back to std size, and then bore it to fit your old piston. Also, I think the 317 and 340 hirths have the same stroke, so if you run across one of those engines, you could swap the top ends or even use the whole engine. The 292, 300, 317 and 340 should bolt right in. It wouldn't be original, but at least it would be running so you can beat on it. Thats it for now, I write more when I find out mor info.

Matt in Michigan

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Re: hirth 300 piston issues

Post by Go Go Diablo » Tue Mar 11, 2008 4:02 pm

Now that's what I'm talking about. People helping people. That's what this forum is all about. Great job Matt!
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Re: hirth 300 piston issues

Post by bottomsupduckclub » Tue Mar 11, 2008 8:11 pm

I'm currently in the process of trying to find someone who can reproduce the pistons we are in need of. The problem so far is that the total cost for a run is around $3500 :o Unless I can find 22 or so others looking for a piston, rings & wrist pin, that's way out of my budget. If we were to find enough people to pony up some $$ we can have the piston made by Wiseco :D

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matt collins
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Re: hirth 300 piston issues

Post by matt collins » Sat Mar 15, 2008 2:20 pm

Wiseco can produce a piston for about $150 if you send them a sample. They have tons of differnt size "blanks" that they can cut to match. Contact them first.

Matt

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Re: hirth 300 piston issues

Post by bottomsupduckclub » Wed Mar 26, 2008 8:09 pm

Matt, I spoke with a sales person a few weeks ago. He stated that they would have to run a small production order of 24, at $145 each. That's what Wiseco told me anyway, so I will not be ordering any unless I can find 22 people who need pistons.
69 Diablo "503"
72 Kitty cat
74 JD 295s (1 1/2X)
7? Jdx8
81 Spitfire
80 Liquifire CUSTOM
94 Indy
94 XCR 440

matt collins
Posts:8
Joined:Tue Mar 11, 2008 11:46 am

Re: hirth 300 piston issues

Post by matt collins » Fri Mar 28, 2008 8:36 am

Ok put me down for one. What oversize were you thinking of going to? I suggest .040 just to be safe. Ok everybody, who needs a piston? I'm sure we can get 24 people to pitch in.

Matt

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