Post by Chuck78 on Dec 20, 2019 3:27:11 GMT
I was considering doing the expansion chamber mod on the 82-84 PE175 to try and make more power out of it, as apparently the sound absorbing perforated metal inner layer in these pipes robs a lot of power on it's own, and is considered a power upgrade to cut the chamber open and remove, not to mention the alleged restrictor washer that is welded into the end of the expansion chamber - presumably to tune what I'm guessing is an RM125 expansion chamber that is effectively shortened to give it more mid range power.
I had also considered aftermarket pipes, all of which at this time in history would have to be custom made my GMC in Australia (Geoff Morris Concepts), a place in Texas that makes custom chambers, or a few other places in the US that I have read about in the past but cannot recall the names of at present (will add later).
Then in search of an article on putting a TS185 piston into a PE175, I accidentally stumbled upon this article which is not what the upper left title says. This is an exert that shows a PE175 section of an article showing all the known common/popular mods to the then-current 200cc class of bikes (by 83, the PE175 was the only one of the big 3 2-stroke Japanese enduro manufacturers that hadn't stepped up from 175 to 200cc).
One of the hop-ups in this article, aside from adding a DS185 piston (basically the same as the TS185), was that they say that they found an RM250Z expansion chamber to be almost a direct fit, with moving a sliding mount around slightly, and grinding on one of the cylinder head fins a bit for clearance... WOW. I would not have expected this to be the case! They said it gave the bike significantly better mid range and low end power, surprisingly to me. Also stating that it weighed half as much as the PE175 expansion chamber (it doesn't have the sound deadening inner mesh/perforated steel layer that the article describes as power robbing).
Has anyone ever tried this?
I may just cut mine open and do the gutting mods myself, as it has 2 dents that I'd like to pop out, and with the inner metal layer, popping out the dents with a pressurization kit + oxy-acetylene would only pop out the outer layer of metal, not the perforated inner layer.
May as well cut & gut it, I have just convinced myself tonight! very thin cutoff wheels will be the trick for this, to avoid altering the chamber much. thin die grinder wheels may be better than hand held angle grinder wheels, as the slightly smaller diameter may offer slightly thinner widths as well. I have a 100 pack of 1-1.4" dremel fiber reinforced cutoff wheels, but I don't think I have that kind of patience, even with my 1/4hp cable driven hanging grinder tool (an awesome dremel on steroids with a flexible cable driveshaft, hang the 1/4hp motor off a hook above your workbench, control the on/off and speed with basically a sewing machine or TIG welding footpedal... a brilliant tool!
I will also be on the lookout for an '82 RM250Z expansion chamber.... much cheaper than aftermarket, and easier to come by quickly I'd assume.
Z = 1982
