The pandemic has delayed our roadrace season a bit here in the PNW, but we are finally on the track again! 2020 has held lots of surprises, including a significant injury for me back in January that I am still recovering from. That said, I am getting serious about my next WMRRA race build so it's time to post up some progress.
I've successfully campaigned :celebrate: in the V250 and V500 classes over the past few years, but it's time for a new challenge. Initially I thought about the V160/175 class, but those losers submitted a rule change to keep 2 strokes out (I think they were sore about that OMRRA guy with the CT-1 that spanked them), so my attention turned to the V750 class......... >:D.
750 Vintage allows disc brakes in WMRRA (and OMRRA) and is dominated by SOHC CB750's with the occasional Seeley-Westlake, Norton, CB720 (550 bored/stroked), GT750, and so on. While a stock CB750 isn't that concerning on the track, most of these are CR750 replicas with fully built engines so it will be a real challenge to bring the fight to the front runners on the DS7. For 2020 I've mothballed the SV650 so I can focus on getting the DS7 updated and dialed in.
To be competitive the DS7 is going to need significant upgrades, but as Kevin Cameron said "Simplicity and light weight are never out of place in racing". On the plus side the DS7 is much lighter than the CB's (268lbs vs. 400+lbs), narrower, has better geometry, and is easier to make it handle well. The negatives are it is down on power (they make 80+hp), currently doesn't stop that well, and gives up a huge amount of displacement for the 750 class. The strategy is simple: a well sorted disc front end so I can charge deep and trailbrake into corners while maximizing my theoretical mid-corner speed advantage AND enough smooth power to get after it before they do on corner exit and stay in the draft on the longer straights. A fairing is also in the works for eking out those last few mph.
The front end is pretty straightforward. I had found set of TX500 forks, triple, and front wheel a while back, so I re-laced the wheel with an 18" rim, rebuilt the forks, put a fresh Conti CR3 on there. Jamie @ Sonic Springs helped me choose a spring rate and they are winding those as we speak. For grins I went with a dual disc setup, mostly so I could use the spare 1st Gen SV650 brake setup I had laying around. We'll see how it works, but I may go to a single disc/RD caliper later on to save weight. Those discs are heavy!!!!
(https://photos.smugmug.com/WMRRA-Racing/2020-Rd-1/i-NCtt7KJ/0/66c7edf5/XL/20200716_182125-XL.jpg)
For the engine I decided to seek professional help. I knew an R5 350cc top end was in order but I was unsure what direction to take the porting and how far. I initially thought about using the TR3 port specs as a starting point, but I was concerned with both the reliability of the engine and my ability to ride it. I reached out to Garrett (GRA2Strokes) for advice and after some conversation about what I was trying to achieve we settled on a plan: He would port the top end, not a full on roadrace port job but something to give me more up top and take advantage of my pipes and a bigger set of carbs. He would also cut the heads and make good use of the high octane fuel I run. Carbs are VM30's, with the spigots turned down to fit in the stock boots.
Before
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After, almost done
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;D seriously love these updates. Thanks for sharing.
So much respect for club racers, even more for vintage club racers, Super extra respect for CB750 killers!
No disrespect to any cb750 riders....
Crankin'! I'm building the new engine on an RD350 lower end I had laying around.
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This one was crusty as hell, but new parts are on the way to get it ready for a new life :vroom:.
Watching from Washington with great interest :pop: go get 'em!
Quote from: 85RZwade on July 26, 2020, 11:53:22 PM
Watching from Washington with great interest :pop: go get 'em!
We'll see!!!! V750 has some serious competition: the combination of well developed bikes and experienced riders means I'll have to work my ass off to catch them. Mick Hart was collecting points and podiums on a factory Laverda long before I was even a thing. But they all do have valves and as we know in the enlightened 2T forum, valves are for toilets. :dawg:
When I raced my modded RD400, way back when, I found the light weight (me and the bike) really helped. Just as much as horsepower for acceleration, slowing down quickly makes for a good lap time. A bike weighing 150 pounds less does that so much better.
A little more encouragement. When my buddy brought his stock Laverta Jota 1000 to the track, the hot rodded RD could accelerate just as quick, if not quicker. Good luck. If those guys with valves are right behind you they are going to have a "holy crap" moment if they try to hold their throttle on as long as you entering a turn. :righteous:
Things are happening fast now :metal:. Garrett has been making chips getting my cylinders and heads together. He is planning to ship them Wed.
Port/sleeve alignment was terrible!
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Ah, much better!
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Also......
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I too have been busy getting my crank together and trued. Cleaning up this case has been a major PITA. Whatever sealant the last person used was really hard to remove! Also this engine was apparently run on castor so it's got that gunk in the crank area.
(https://photos.smugmug.com/WMRRA-Racing/2020-Rd-1/i-WvtcBwP/0/6aa099a6/L/20200801_101742-L.jpg)
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Sorting jets is tedious..
(https://photos.smugmug.com/WMRRA-Racing/2020-Rd-1/i-qSrCxfM/0/3caf987e/L/20200728_195005-L.jpg)
Are you guys allowed to do any serious port work?
Quote from: Czakky on August 04, 2020, 09:19:53 PM
Are you guys allowed to do any serious port work?
Yes, engine modifications are open. They do need to be reasonable for the period (no flatslides, etc.) and adhere to the displacement limits.
So, I got a box of parts from Garrett.......
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Nothing too crazy here, but they do look nice! I wonder how they run? Only one way to find out :vroom:
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Assembly and squish measurements. My base gaskets were a little thicker so the squish ended up at 0.038" (was shooting for 0.030").
(https://photos.smugmug.com/WMRRA-Racing/2020-Rd-1/i-HCXQTnW/0/3f493bad/L/20200809_123104-L.jpg)
Got my carb situation sorted out using an RD350 high top throttle junction and cables, plus a spacer that I machined. I will be running the cables that John @EC sells specifically for this combination after the upcoming race round.
(https://photos.smugmug.com/WMRRA-Racing/2020-Rd-1/i-XcCXZhC/0/d5779868/L/20200810_114835-L.jpg)
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Then we were here! Did some jetting work today and I am pleased with the results. This thing rips! I can't wait to get it on the track. Now to get my numbers back on and finish the safety wire.
Looking good!
Garrett does great work! The porting and head work he did on the Kart Track Racer project bike ripped. :metal:
Can't wait to get back into the LC he worked on for me.
Light weight, big ports and carbs, super brakes. That thing is going to perform. :clap:
This has been a great project and will be a continuous effort to study different effect and gains. We started off with a very mild port job actually. Naturally there will be many gains just by removing bad miss matches. On the transfer the miss match was so terrible it actually barley blended at the desired height I set.
I have another set I will be much more aggressive on and of course my pipes will be going on as well. That's the next immediate step.
Garrett
What a weekend! I was a little apprehensive because I didn't have much time on the bike and there have been a lot of changes: different front end, front brakes, tires, top end, primary ratio, 6 speed...etc. Even the track was different since The Ridge added a chicane to the front straight. But in the end, there is only one way to get a bike sorted: go ride it ! :vroom:
It was hot for WA this past weekend, 98F in my pits that afternoon. First practice went well: I didn't hit anybody or fall down, plus the bike didn't seize :dawg:. All my shift & braking points were different so I spent most of the time feeling out where I could use my newfound power and how to keep the engine above 7.5k rpm so I could get good drive out of the turns. Once I got that worked out I began pushing my braking points closer and doing more trail braking. In all of this I neglected to do a practice start... doh!
1st race: I got a terrible start (see above mistake) :'( and the rest of the 750 pack zoomed away. This engine/carb combo is not the easiest to launch and I need to practice that more. I worked my way up to 3rd place behind Duncan's Seeley-Westlake but didn't really have a solid move in mind to get by him so I tucked in to learn his riding style and get a plan. Then in Lap 4 he went wide in T6 (big carousel turn) just as I was practicing closing up on him at corner entry, so I swooped in for a clean inside pass and got on the gas early. I knew he was slower through T8 so I blitzed through there at svelte Yamaha twin appropriate speeds and gapped him. He reeled me in a bit on the WOT run to T11, but I went in deeper and used T11-16 to pull a big gap. Since they added the chicane and shortened the front straight, his straight line pull was less of an advantage and I maintained the position to take 2nd. The 1st place bike was on a CR750 replica and was waaaay out front.
2nd race: I got a better start and left with the pack. The winner of the 1st race was out with a mechanical issue so I got to thinking that I might be able to win if I got my head screwed on straight. Of course, Duncan had the same idea so I worked my ass off to try and pass him. By the start of Lap 5 I was ready to accept 2nd place: I was hot, tired, beat, and didn't have much left. Right about that time Duncan got on the binders early for the chicane so I stepped out of his draft, braked late, and made the pass entering the chicane. I hodged up the turns but he did as well so I didn't immediately get passed again and now had clear track. I put the burners on, gapped him through T2-4 and consolidated 1st place :toot:
Garrett and I have lots of work to do to develop this bike and engine, but it was a great start! I can't thank him enough for sharing his experience and skills to make this happen :clap: . I am tired, and that's all I've got for now.
Chasing Duncan through the chicane
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Fantastic writeup Stephen!
Pretty sure my buddy Austin McCabe (snaggletooth77x on here) was up there on his 690 powered KTM 390 racing against the Kramers.
Quote from: pdxjim on August 17, 2020, 04:48:07 PM
Fantastic writeup Stephen!
Pretty sure my buddy Austin McCabe (snaggletooth77x on here) was up there on his 690 powered KTM 390 racing against the Kramers.
He was! 3 pits down from me. I saw his dirty & beat up KTM loaded in a pickup so I think he binned it at some point during the weekend. The Kramers are fast for sure, but it was fun to see DiBrino mow them down with an old SV650. That guy is un-freaking-believable.
That is just :whoop:. Well written write up, thanks for that.
Quote from: idr5c on August 17, 2020, 05:23:35 PM
He was! 3 pits down from me. I saw his dirty & beat up KTM loaded in a pickup so I think he binned it at some point during the weekend. The Kramers are fast for sure, but it was fun to see DiBrino mow them down with an old SV650. That guy is un-freaking-believable.
Yup. Just got the rundown.
Austin had a massive highside in T12 on Saturday.
... and yeah, Andy did our Bol d'OR 6hr Endurance on a EX300 a few years ago. Very fast, but way too serious for the spirit of the race. He's fast AF on a flattrack and mx bike too.
Congrats on the successful weekend on the new iteration of the bike. :clap:
Wow, excellent results for the maiden voyage, sounds like the R5 will dominate. :clap:
Quote from: 1976RD400C on August 18, 2020, 05:51:54 PM
Wow, excellent results for the maiden voyage, sounds like the R5 will dominate. :clap:
We will see, some of the fast CR750's didn't make this round but I least I know what to shoot for.
Another race weekend done! Overall it was a success, but it didn't start out that way..... :umm:
Round 5 was at Pacific Raceways so I had a few things working against me: Pacific is a fast, flowing track with a long straight (compared to The Ridge) and my competition has been racing there much longer than I have. I really enjoy Pacific but I'm usually not as competitive there for some reason. For extra practice and setup time I signed up for the track day on Friday.
I spent most of Friday coming up to speed and figuring out my shifting/braking points. I was not as "on it" as I had hoped. With the new tires I'm still working up to pushing the front hard since the feedback they give is quite different than the Avons I've raced with prior. Duncan towed me around a bit and I got the back section put together well so I could carry lots of speed. My big competition for this weekend was a couple of well developed Nortons (+70hp) and a CR750.
I continued to dial things in during practice on Sat and Sun, did some practice starts, and then prepped for my races. The CR750 was off pace for some reason so I had that going for me. In the 1st race I boned the start (dammit! :bang:) and ended up in the back. Have I mentioned how difficult it is to get a good start with this engine? Anyway, I put the burners on and started passing people and closed in on the Nortons occupying 1st and 2nd place..... but then we came to T10 and went out onto the straight where they zoomed away. I reeled them back in during the next lap but they pulled me pretty good on the next straight. And so it went, lap after lap. I pushed until I almost binned it in T9 and at that point I realized I had a secure 3rd... maybe it was time to go for the bronze.
I got a much better start in Race 2 and used the fortuitous presence of a DOHC CB750 to box out one of the Nortons into T1. I put my head down and really pushed: late into T3, fast momentum lines through T5-6, sliding the front on the exit of T7, flat out through T8, and made it over halfway down the straight but the Norton would not be denied and he came zooming past. The chase had also lit a fire under his ass and he put in some solid laps afterward so I wasn't able to challenge him again. A lonely 3rd it was.
Not a win this weekend, but I didn't fall down OR hit anyone so that's a success I would say. More refinements will be needed.... stay tuned...
Trackday fun
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Chasing the Nortons out of T10
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On to the straight
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Rolling onto the throttle out of T2
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And a hot air ballon landed at the track!!!!
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:cheerleader:
Nice job....How modified is your porting? Is it pulling hard in the 7-10K range? What rpm are you shifting at? You think you can get more HP out of it? :thumbs:
Quote from: 1976RD400C on September 09, 2020, 04:10:17 PM
Nice job....How modified is your porting? Is it pulling hard in the 7-10K range? What rpm are you shifting at? You think you can get more HP out of it? :thumbs:
I ported his engine and cut his heads. We are working on this in stages. This is just the first stage. I started off with a little to much intake timing on this setup but can easily be corrected with less of a window cutout on the piston. We will develop this engine over the season.
He also just got a set of scratch and dent pipes from me to get some feedback to me over his spec 2 classics.
Garrett
Well done all round guys.
Makes great reading too.
Sent from my SM-G973F using Tapatalk
great reading
interesting to hear there are lots of development plans for the future
and great to see 2strokes taking big 4's.
A bittersweet time, the 2020 WMRRA season comes to a close :( We were suppose to have a joint race round with OMRRA at PIR Sept 26-27th, but they bailed on us so our final official round of 2020 was cancelled. Disappointing to say the least but that's how it goes. I was feeling good about the round: Garrett's pipes and the fact that I have more laps at PIR than many of my 750 compatriots made me think I had a shot at mopping up the V750 class but I'll have to wait and try again next year. It's not official yet but by the points I ended up in 2nd for the championship :whoop:.
And so the story ends................ or does it? :evil2:
Faced with no circuit racing prospects I did what any self respecting racer would do: signed up for the Maryhill Loops Road vintage hillclimb!!! This event is put on by the Maryhill vintage car club and they welcome those of us with old bikes. It's an incredible experience, but very different than circuit racing. The "send it" mentality has no place on a road like this.
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Lots of cool cars were there, I especially enjoyed the Bentley.
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When all the runs were tallied up I came out with the 2nd fastest V750 class time!!! :righteous: :metal: I was pretty stoked about that, having never run the course before.
(https://photos.smugmug.com/photos/i-vqg22vx/0/XL/i-vqg22vx-XL.jpg)
And now the season is truly done. I owe Garrett some data regarding the engine and pipes and we need to develop our game plan for 2021. I expect a fairing, better ergos, and porting refinement will be part of that. I need to thank Garrett and the forum for helping make my race results possible :clap:. As always, if you have an interest in motorcycle racing send me a message and my pit is always open. Until next time!
Looks like a really fun event and road! Looking forward to hearing your updates next season. :cheerleader: