Darrins 985 motor build with Dyno chart and 114.75 RWHP

Posted: Wed Apr 27, 2016 2:09 am

I used CBX pistons and cut the deck. Like the Ledar article. Don't know how it worked yet. It worked in that article, should work for me. I don't do alot on my own I just copy things that seem like a decent idea. I was going to go without a base gasket but the motor guy around here did remind me it's a street bike. Was another .020 off the deck though.

Peoples ideas I used, JJam, Captain, Bobcat7, Ledar, NathanHouse, Melchiro, Sonicrete, Headless and mine.

Tried to do it cheap, didn't work out. Wasn't crazy, just wasn't cheap.

Toddk

Posted: Wed Apr 27, 2016 4:21 am

Hey guy's,
I have been in California at Willow Springs to watch Darrin race and help with the bike.
It ran flawless all 3 days. Darrin went 8 seconds a lap faster then he ever has and the only bike change was the motor. I was very happy.

He got a couple 4th's on Saturday and reeled in two second place finishes on Sunday. It was a great weekend and now I have my first full race under my belt. Lots of things were learned and I am already building the next motor for my race bike. It will be from parts that I have in the shop to keep the cost down. I plan to build a Phillip Island motor and it will have to be a 1187cc to be competitive with the monsters that are allowed over there.

In the mean time I plan to be at Barber Motorsports in October and if all goes well I'll make it to Millers in September as well?? Time and money will decide what goes on.

Here is the plan for the first motor. It will be an 888cc short stroke.

1100 cases with all of the oiling mods including the reverse oil mod.
1100 rods sleeved down by Nathan House to fit 15mm wrist pins and new 1100 rod bolts.
67.5mm Wiseco pistons that I will modify the domes to fit in the Super Head that I bought from Brent and the Zanzanis. (the pistons will not have a low deck height because the 1100 rods are longer. I will use a spacer plate and proper thickness of base gaskets to achieve a zero deck height).
I will be using a 750 crank with stock 750 stroke and I'll lighten the crank and have it balanced as well.
I'll be using a 750 set of barrels as well and may even install some thicker sleeves as I already have them for the 67.5mm pistons.
The head will be my Hyde head.
Cams will be Web 110 with under the bucket shims and dual valve springs.
Carbs will be 35mm as per Brents suggestion for this head. If by chance the carbs are to large, (won't know until it gets dyno tested) I'll use some VM33's that I have on hand?
Transmission will be 1000C.
Clutch will be a 900 set up with a banded basket, welded up clutch pusher, EBC plates with an extra steel plate and throw away the riveted steels. It will also get a 1100 pressure plate as they are stronger.

Anyway, I have a lot to do in the next few months. Trying to fit in my bikes into my work schedule is a major problem as I never have enough time. Go figure. Ha.

I believe that this 888 will make more HP then the 985 because of the head, cams and carbs?

Peace, Jim

Posted: Wed Apr 27, 2016 4:25 am

ex-ama-superbike wrote:

From the AHRMA rulebook....."A restrictor plate may be used where a minimum carburetor size is speci ed. A re- strictor plate must be at 1/8-inch thick with a constant diameter bore no larger than the required maximum diameter."........nice job on that engine!

So your saying the re-stricter is 1/8" wide or you mean it has to be 1/8" thick? Sorry but I got lost on that one.

I'll build a 1020cc if this is true?

Peace, Jim

Posted: Wed Apr 27, 2016 11:55 am

I think you may be right! Sounds like a stout setup!!

Posted: Wed Apr 27, 2016 2:37 pm

JJam wrote:

ex-ama-superbike wrote:

From the AHRMA rulebook....."A restrictor plate may be used where a minimum carburetor size is speci ed. A re- strictor plate must be at 1/8-inch thick with a constant diameter bore no larger than the required maximum diameter."........nice job on that engine!

So your saying the re-stricter is 1/8" wide or you mean it has to be 1/8" thick? Sorry but I got lost on that one.

I'll build a 1020cc if this is true?

Peace, Jim

The plate you make the restrictor out of had to be at least 1/8" thick/wide and the restrictor hole/opening can only be 29mm. If you put a 1/8" thick plate in the carb insulator and sandwiched it between the insulator and the carb mouth with a 29mm opening, that would satisfy the rules. If you were able to place that plate anywhere in the intake tract after the carb venturi and before the valves, that should satisfy the rules provided it at least meets the minimum thickness of 1/8" (it could be thicker) and has an opening of 29mm diameter (it could be smaller) then you've satisfied the rule's intent.

Posted: Wed Apr 27, 2016 3:36 pm

Do you think you can speed up the intake charge by inserting a tube in the spigot side of the carb or would it drop off after entering the insulator?

Toddk

Posted: Wed Apr 27, 2016 3:47 pm

toddk wrote:

Do you think you can speed up the intake charge by inserting a tube in the spigot side of the carb or would it drop off after entering the insulator?

Toddk

Or, build a tube that inserts into each insulator that is shaped like a venturi, with the smallest diameter being the 29mm Question

This of course means that you must start off with straight tube insulators ..... which Jim would be since it's one of Captain's heads.

Posted: Wed Apr 27, 2016 6:02 pm

toddk wrote:

Do you think you can speed up the intake charge by inserting a tube in the spigot side of the carb or would it drop off after entering the insulator?

Toddk

Looks like I need to get my flow bench up and running. Then I could test many different designs out??? So much to do and so little time.

Peace, Jim

Posted: Thu Apr 28, 2016 2:04 am

Shawn_Mc wrote:

ex-ama-superbike wrote:

From the AHRMA rulebook....."A restrictor plate may be used where a minimum carburetor size is speci ed. A re- strictor plate must be at 1/8-inch thick with a constant diameter bore no larger than the required maximum diameter."........nice job on that engine!

Right out of the AHRMA rule book for Vintage superbikes.

Quote:

3) All round-slide carbs are allowed (Keihin CR, Dell’Orto, Mikuni “smooth
bore” and like design). Flat-slide carbs are not allowed. Pumper carbs may be
used, but the pumper mechanism must be disabled. 1025cc four-cylinders [b]may
use carburetors up to 29mm, or the stock constant-velocity carburetors that
were original equipment on that machine.[/b]

This limits you to 931cc, or 29mm carbs.

I think there's power to be had in the OEM CVs when setup properly at 1025 ccs.

The 29mm restrictor only applies to the classes above the Vintage superbike.

If you took the OEM offered CV's and bored them straight through, and modded to suit, I think there's HP there. More HP than available with the 29's. Especially since you could get pretty close to 37-38mm on those CV's.

Read that rule closely. It doesn't say an unmodified carb, it says original equipment. Its sentences like these that led to 700 hp "Stock" 427 Chevys in Boat racing.

Posted: Thu Apr 28, 2016 2:39 am

No it doesn't......re read the rulebook.

Posted: Thu Apr 28, 2016 7:14 pm

Personally I think that rule is bull shit! This is supposed to be historic racing and that vintage superbike was allowed 31mm carbs or 33mm necked down. The smallest carb listed in the Sudco catalog for a CB900F is a 31mm. I have a period correct superbike that was raced in the day that is not legal for its historic class….just don’t get it!

Posted: Fri Apr 29, 2016 7:39 pm

That whole general section that you say applies only to vintage classes applies to vintage superbike as well.I won't argue that maybe AHRMA should clarify,that's a different discussion.I'm sure a the guys who ran 33 mik's on their Z's in this class would never have gotten away with it if my interpretation was wrong.

Posted: Fri Apr 29, 2016 7:43 pm

Believe me,I'd like to be wrong,then I could live happily ever after with the 2 sets of too small,new, 29mm cr' I'm stuck with.2 piston calipers are a bogus rule as well.The carb rule should be clarified.