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Anyone here have real first hand experience with the mid 70’s Noguchi performance kits for YZ’s?
I have an authentic NOS Stage 2 Noguchi cylinder ,piston and rings that I’ve been reluctant to put on our 74 YZ125 (that has a Yamaha 175 top end). Does anyone have an idea if those cylinders actually produced a noticeable power increase like has been rumored? Looking at the porting on both, it looks like the Noguchi cylinder is actually more restrictive than the stock Yamaha cylinder
Any help would be appreciated as I don’t necessarily want to “deflower” the Noguchi pieces unless it’s going to be worth it.
I have an authentic NOS Stage 2 Noguchi cylinder ,piston and rings that I’ve been reluctant to put on our 74 YZ125 (that has a Yamaha 175 top end). Does anyone have an idea if those cylinders actually produced a noticeable power increase like has been rumored? Looking at the porting on both, it looks like the Noguchi cylinder is actually more restrictive than the stock Yamaha cylinder
Any help would be appreciated as I don’t necessarily want to “deflower” the Noguchi pieces unless it’s going to be worth it.
At the end of the 74 season, District 14 put me in "A" class for 75. I was convinced by the Yamaha shop I bought my bikes from I needed more HP and purchased the 125 kit W/O the pipe and carb (non were available) for my 74 YZ125. I worked hard to get it to run well enough and never could. When I was recommended by the Factory race team with the help of the Yamaha shop owner to put a 34mm carb and a just released 76 up pipe on it, it just screamed! Timing still stock, once properly jetted it was as fast as any modified Honda, Suzuki, from all the big-name tuners around the Midwest. I raced a 74 YZ250 also in 75 and I was very happy on how both of them ran for me. No extra porting was performed on the cylinder, I just polished the exhaust. They were a great upgrade.
Anyway, Laci runs the Womens Expert division in Vintage ( 74 and prior) and Post Vintage 75-to 84? . Womens classes have no limit on displacement. She’s ran against girls on TM 400’s,big bore Husky’s etc etc . ( in a year and a half she’s still undefeated lol) We kind of measure her successes against the mens classes that are on her gate and she typically finishes in the top 3 against the guys, and has won several.
I have a Jemco cone pipe on the Yamaha with a PVL, stock reed cage, but I have a Mossbarger 6 petal that doesn’t fit the cylinder (you’re right on the fact that those 74’s have a small intake tract.) wonder if there is enough material to machine out to accept it? I made a custom aluminum air box with a LOT of flow . We run a 100/100 -18 Pirelli on the rear. And I agree those webco heads are very effective in keeping that little screamer cooler than other heads
I like the idea of running a 76 cylinder, but that would be outside the rules,lol
Was the stock carb a 28?
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I’ve been offered $ 2150 for the kit, but it’s not for sale , BUT …. once I put it on and try it , the value will drop dramatically. If it’s a total screamer ,great….. if not , ithen my super rare NOS kit is now just another used one.
Im going to probably try what RD confirmed for me above, I’m going to do a little porting work on the existing 175 cylinder, go with a 30 mm Mikuni and hog out the intake to use the Mossbarger 6 petal reed block.
I do have a modified 74 YZ250A in the stable, if alll else fails…
All of which is to say that Jon probably built that cone pipe for the stock port timing/size, and in your shoes, I would mess with port timing last. First tend to matching/cleanup, especially at the exhaust manifold junction to let the pipe work optimally, then really focus on uncorking the intake as you are already leaning towards.
A 28mm Mikuni seems awfully small for the 175 cylinder, when the same-gen 100 had a 26. One thing I only grasped recently was that when reed valves were new, most of us marveled at not loading up + a little torque off the bottom, but tuners were really using them to extend top end on small bores like Hodaka 100s, as reeds could allow as much effective intake duration as the engine wanted. An undersized carb restricts that effect, and more reed capacity may help there too.
So knock yourself out opening up the intake capacity, incrementally if possible in case you go too far. It's strange that a 30 or 32mm won't fit the stock rubber manifold, but then again, things like that are what gets compromised in production.
Hopefully it screams further on top without hurting anything else, which reminds me of what may be a dumb question, what about track-specific gearing? That seems imperative when running the open-displacement class. I realize you probably regeared it already, but another wheel + chain for a gearing change, even another countershaft sprocket + chain? Whatever lets her start well + ride tactically ditto, on each track you race. That's something I would go out and test locally so she knows what the option feels like, to tighten up or spread out the power, or what makes starts most consistent. Another wheel 2 teeth different that helps at some tracks is cheaper than a $2150 top end.
Apologies for completely digressing from Noguchi top ends, but I am going by my fond memory of Jon's LT-2M pipe on my 100, which must have screamed 1500 rpm higher without changing anything else, or losing anything down low. That was a great example of unlocking what the stock porting and intake allowed.
The gearing we messed with already and found what works for most of the AHRMA moto tracks we’ve run across, but that will likely change too if the cylinder mods and carb work as I hope.
In the big scheme of things,I probably shouldn’t even mess with it too much,as even in the Expert division,no women have given her much of a struggle,but she does like to beat the guys in whatever other class may be on her gate . That being said it’s hard for me not to tinker and try to make things just a LITTLE bit better on all of our bikes ,lol.
Keep in mind that she is no kid at 32 and just started racing 18 months ago,so I’ve been taking baby steps with her bikes but it may be time to cut her loose
Thanks Speedman for the post.
Any chance I can get jetting specs from that 34 Mikuni??
Thanks, Gary Moir
Garymoir,
I don't have documentation from back then I just leaned the pilot, needle (clip) by small increments and the main until I had it. Find the stock jets that was in the carb on a 74 YZ250a from Yamaha web site and go from there. Good luck.
Agree with Bbit above. I had ordered the carb from Chad at Sudco (before they closed up) it was jetted with the stock jets for a 250A. It actually ran almost perfect. However my Noguchi cylinder we ended up using was a highly modified Stage 2 . I had in depth conversations with Dave Townsley ( he was the sole US distributor for Noguchi back in the 70’s) he educated me dramatically on all of the Noguchi products— the “off the shelf” pieces that were sold to the public AND the factory pieces that Japanese team used . Dave spent a lot of time with Tanehanu Noguchi in Japan and helped develop the race teams bikes . Anyway my stage 2 175 cylinder was modified to those specs , using a modified Noguchi head, PVL ignition , the Sudco/ Mikuni ( NOT the small body ) a huge, modified 6 petal Mossbarger reed cage and a Geoff morris pipe. Obviously had to fab a new airbox as well. I had John Bushby fabricate another set of his billet triples that pull in the front end and make the bike turn exceptionally well ( we use those on all our YZA’s) as we do with the KLP alloy arms - Karl makes them 1” longer . That combo of the pulled in clamps and longer swingarm push the center of gravity closer to the front and these bikes handle extremely well. I actually just finished this particular bike a couple weeks ago and did some heat cycles and a few mid~upper throttle laps at our home track , and that bike is absolutely WICKED . It really feels as strong as our 250A’s . Anyway sorry for going off on a tangent , but yes go with the stock 250 jetting specs and fiddle from there.
Not the best picture, but this was my Noguchi I bought from my friend Gene McKay. It had a 175 kit that was ported and built by his Japanese mechanic “Hochi” (probably spelled that wrong). It was a rocket and I won several races on it in the local pro class that was 0-200cc so it was legal.
There used to be a Noguchi warehouse near Stone Mountain in GA. We’d pass it on the way to the park. Huge blue letters on the side of the building. Mid 70’s.
Noguchi experts, I have brochure for YZ items if anyone is interested, Also Noguchi decal.
I’m interested in the Noguchi items. Sending you a message.
That would have been Dirty Distributing, the Noguchi distributor for the U.S.
YZ302, I will add some Yamaha stickers and get the Noguchi stuff out to you this week.
Pit Row
Dave Townsley (Dirty Distributing) is still around . I've talked to him several times over the past few years and he gave me a wealth of great info that wasn't generally known . Good dude and extremely helpful sorting out 'fact' from 'fiction' on the Noguchi pieces
Awesome! Thanks.
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