While studying Penton photos,I've noticed that some have stays that are attached near the top of the frame and to the top of the crankcase and others don't. Is this specific to certain models? Thanks
I am supposing that you are talking about the KTM motors. Some might be tempted to run the bike without those stays but that would be a mistake. you may have seen some bike like that. I realize that having them there makes it difficult to do any maitainence on the bike but they are needed. It helps to further trianglate the frame to provide more support. In addition, running with out them puis un due stress on the motor mounts. I have seen lots of things done that I am sure would make the designers of those bikes pussled as to why it was done. frankly lots of things that are down right scary. I don't think this rates scary but in my mind foolish to go with out those stays, if your bike does not have them, get some.. Just my two cents.
Thom Green,Still crazy after all these years!
76' 250 MC5 (orginal owner)
74' 1/2 440 maico
70' 400 maico (project)
72' cr125 Husky (project)
93' RMx 250 suzuki
My first experience with engine support stays, or the lack of, was on my '76 250GS/7 Hercules. These were known vibrators from the time they first came into the country. They have a bath tub style crank case, bottom and rear engine mounts, with no front mounts or engine stays. The engine just kind of hangs out there by the bottom and rear mount. The bottom mount plate is inadequate and acts like a spring board. Every time the piston goes up and down and the ignition fires the result is a bad vibration. Oddly enough, the 175s had the top engine stays that stabilized the engine, and later, right near the end of production, they added a front engine mount to the 250 that helped a lot but they are rare. I asked why the 175s had the cylinder mounted stays but the 250s did not, and the answer was, no room for them. I combated the vibration problem with constant vigilance of the mounting bolt tightness, and oddly enough, at the '03 ISDTRR Billy Uhl gave me a tip about tightening the swing arm pivot bolt as tightly as possible and that all helped. One weekend while prepping the bike for an upcoming ISDT Reunion Ride, I saw a way to mount the cylinder stays on my 250. I acquired a set of the proper nuts from Speedy and installed them on the cylinder, fabricated the stays by copying the units from my 175 Herc and installed the one on the left side as per usual, and installed the one on the right side by drilling a hole in the frame gusset near the steering head, and ran that stay towards the front. it still kept the already mentioned triangulation effect and I could still reach the carb and spark plug. And it cut down the vibration to a much more tolerable level. No single cylinder two stroke engine is going to run like a sewing machine and will vibrate. I think if the KTM engine wasn't mounted like it is it would tend to vibrate a lot worse also. I even have a '72 Hodaka Wombat that had them from the factory! So if you are contemplating to use them or not, I also would encourage you to not exclude them.
Type at you later,
Dan McEntee
Some Pentons with Sachs engines came stock with the frame-to-engine brackets. My 1974 Penton Berkshire had them. joe
The bike is a 74 six days with a 125 Sachs engine. The mounting holes look like they have had bolts in them at some time but there wern't any stays with the bike. In looking at photos I saw them with and without so was just curious. Thanks for the replys.
Neither of my 100s had them. I have seen them in pictures, I have never seen them on a Sachs in person and every KTM engine bike I have seen in pics or in person has them. I dont believe the Sachs needs the support braces.
Brian
My 72 Six Day has them....
Steve Minor
Wilmington, NC
1972 Six Day
1977 125 GS6
1977 400 GS6
1978 400 MC5
My 72 also has them. Hank
Hank Rinehart
My 74 Bershire had them on both sides of the frame to engine case until the first time I serviced the carb.
Back "in the day" we routinely removed them from every race bike and had no problems. We also had impeccable maintenance programs on our bikes.
That said - on 400's if you remove them you have to pay extra attention to keeping the motor mounts properly torqued after every ride (even back then we checked torque on every fastener weekly).
We need to remember - these bikes were engineered to withstand riding the ISDT (not "E"), which exceeded 200 miles per day for 6 straight days with only minimal maintenance possible. In other words they were engineered far greater than needed for the average user.
Riding them in local enduros, and now AHRMA creampuff playrides does not subject them to any where near the stresses they were designed for (unless you don't maintain your bike).
If I were building a concours type showroom replica I would want the stays (or if I was capable of racing a 400 at it's limits) - otherwise I would put those pain in the patooties in the same place I put all the other ones that I removed back in the 70's.....
_____________________________________________________________________________________
"We the willing, led by the unknowing, are doing the impossible, for the ungrateful. We have done so much, for so long, with so little, that we are now qualified to do almost anything, with nothing."
1972 Penton Berkshire 100
1983 Husqvarna 250 XC
2011 Jayco 31.5 RLDS
2009 Chevy 2500 HD Duramax
Even with the stays you need to check all the motor mounts and top end parts for proper torque after every other ride on a 400, those things will shake themselves apart.
Brian
Thanks again for the responses. I really enjoy reading the first hand experiences from"back in the day" I too spent time back then but I don't have personal experience with the Penton bikes as I don't recall any in our area.I worked at a dealership that sold Honda,Norton and Ducati and a friend of mine had the BSA dealership.We didn't have big time races here,more local and regional unless you wanted to travel some distance. I did race some Hondas and a Benelli.