Author Topic: Gentleman's Express 550 engine build (Read 40750 times)

Justin · « **Reply #50 on:** November 27, 2015, 01:22:59 AM »

This thread is awesome, both for the mechanics and education of Honda's CB fours and because of the history you've seen and remembered, Mark. Cheers

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flatlander · « **Reply #51 on:** December 05, 2015, 08:01:21 AM »

great info and stories, hondaman! it's this kind of posts that i was hoping for when you started this thread

HondaMan · « **Reply #52 on:** December 09, 2015, 06:37:18 PM »

I finally got the upper case back on Monday. I have to scrub off the soap scum from the shop's cleaning process so I can paint it and the cylinders. Got the parts all in one place, except the pistons I have to mod. That will be next - with pics!

GV1390 · « **Reply #53 on:** December 10, 2015, 10:06:57 AM »

We need more pictures sir! Sounds great so far.

MRieck · « **Reply #54 on:** December 10, 2015, 12:12:47 PM »

The 550 ports are very choked with huge guide bosses in both the intake and exhaust ports. The lack of total port volume really needs to be addressed to take advantage of a 20% increase in displacement. It also needs the largest valve you can get in there and appropriate seat boring to match the valve. That is what I have found with successful large bore 550 engines.
What do expect for peak HP and at what RPM?

HondaMan · « **Reply #55 on:** December 10, 2015, 07:16:49 PM »

Quote from: MRieck on December 10, 2015, 12:12:47 PM

The 550 ports are very choked with huge guide bosses in both the intake and exhaust ports. The lack of total port volume really needs to be addressed to take advantage of a 20% increase in displacement. It also needs the largest valve you can get in there and appropriate seat boring to match the valve. That is what I have found with successful large bore 550 engines.
What do expect for peak HP and at what RPM?

The RPM will be in the 10k neighborhood, running the CB650 cam. Since it's going to be a mostly-city, street-ride (East Coast) machine, I'm not going too wild with the tuning parameters as it will have to idle in city traffic and need some good low-end grunt. It's pretty easy to make these into high-end-only engines, due to the small bores, so I'm going after it with the "mid-power think" approach. The stock intake valves will help in that regard, and I'll be pulling the intake open somewhere in the 3-8 degrees realm, depending on how well it starts up cold. This will push the start-of-torque down a little in the RPM range so it won't feel so 'flat' like most of the Mid-Fours often do. The extra duration of this cam, the higher compression, and the (TBD) pipe selection will determine the top end range.

The 500/550 has always been a 'gentle beast' at less than 4500 RPM. The main purpose of this exercise is to change that personality.

GV1390 · « **Reply #56 on:** December 10, 2015, 07:33:32 PM »

Anyone have a general idea of the hp this will make roughly? Just curious if anyone has done something similar. Sounds rad so far.

hsas.69 · « **Reply #57 on:** December 10, 2015, 07:51:13 PM »

This is exactly what ive been looking for

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bwaller · « **Reply #58 on:** December 10, 2015, 08:09:58 PM »

Quote from: GV1390 on December 10, 2015, 07:33:32 PM

Anyone have a general idea of the hp this will make roughly?

50ish.

flatlander · « **Reply #59 on:** December 10, 2015, 11:27:21 PM »

Quote from: HondaMan on December 10, 2015, 07:16:49 PM

Since it's going to be a mostly-city, street-ride (East Coast) machine, I'm not going too wild with the tuning parameters as it will have to idle in city traffic and need some good low-end grunt. It's pretty easy to make these into high-end-only engines, due to the small bores, so I'm going after it with the "mid-power think" approach.

hondaman i'll be very interested to see what you get with your setup!

i had similar requirements for my 550. for comparison/inspiration's sake, this is what i did: http://forums.sohc4.net/index.php/topic,134863.msg1719759.html#msg1719759
came out with 54 rwhp and 68nm of torque.

HondaMan · « **Reply #60 on:** December 11, 2015, 07:03:59 PM »

Quote from: bwaller on December 10, 2015, 08:09:58 PM

Quote from: GV1390 on December 10, 2015, 07:33:32 PM
Anyone have a general idea of the hp this will make roughly?

50ish.

That's really interesting: the 750K4-K5 bikes often dyno'd in at 55-58 HP in the mid-1970s. This was mostly due to the detuning they went through in those days, to raise the MPG and increase the midrange torque a little, since the speed limit had dropped to 55 MPH then. If this scoot makes that kind of actual HP in the much lighter chassis, it should really wake it up!

I remember dyno runs on the 550 (I think it was a K2) that pulled just 38 HP at 7800 RPM, peak. They were pure-stock, 3000-ish mile engine runs. That bike would zip up (on the street) to 96 MPH, then creep up to 105 if you laid down on the tank. It was box-stock, and all 4 pipes.

Justin · « **Reply #61 on:** December 12, 2015, 02:50:55 PM »

Is this at sea level? I didn't realise how hard it is for vintage bikes to do the ton.. When I return home I need to rejet my wife's CB360, I thought surely it would do 100mph but it struggles to do 75-80mph out here on California roads

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hsas.69 · « **Reply #62 on:** December 12, 2015, 03:19:14 PM »

My F3 will do the ton no problem, dies off after that though. Have had it up to 115 but was struggling after 100. Cant wait till spring to see what the 550 will do.

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Justin · « **Reply #63 on:** December 12, 2015, 03:24:13 PM »

Quote from: hsas.69 on December 12, 2015, 03:19:14 PM

My F3 will do the ton no problem, dies off after that though. Have had it up to 115 but was struggling after 100. Cant wait till spring to see what the 550 will do.

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Sorry for the thread jack, Mark.
I'm going to have to throw a leg over my brother's F3 and see what she can do. I'm certain she would do the ton, can't wait to see what these here 500/550s will do after Mark's magic

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HondaMan · « **Reply #64 on:** December 12, 2015, 04:28:23 PM »

Quote from: Justin on December 12, 2015, 02:50:55 PM

Is this at sea level? I didn't realise how hard it is for vintage bikes to do the ton.. When I return home I need to rejet my wife's CB360, I thought surely it would do 100mph but it struggles to do 75-80mph out here on California roads

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Justin: send me an e-mail at my Gmail (Hman750@gmail.com) and I'll send you a document to use on the 360 that will probably help: it's about their spark advancers and weak spark as the result. The 350 twin could kick the 360 into a corner, that's for sure!

Camrector · « **Reply #65 on:** December 12, 2015, 05:27:01 PM »

Send me that article about the 360 too Mark! Going to be dropping gs850 pistons in her soon.

Jerry Rxman Griffin aka MuthaF'er · « **Reply #66 on:** December 12, 2015, 07:21:45 PM »

F3 what? If it's a F3 CB750 it should do 'the ton' wound out in 3rd gear!

hsas.69 · « **Reply #67 on:** December 12, 2015, 07:28:14 PM »

Its a 750. I havent finished jetting the carbs yet. Every time i get close i decide to change something else and have to start over.

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HondaMan · « **Reply #68 on:** December 12, 2015, 07:37:44 PM »

Quote from: Jerry Rxman Griffin aka MuthaF'er on December 12, 2015, 07:21:45 PM

F3 what? If it's a F3 CB750 it should do 'the ton' wound out in 3rd gear!

I'll bet yours will do it in 2nd, Jerry!

Jerry Rxman Griffin aka MuthaF'er · « **Reply #69 on:** December 12, 2015, 07:46:28 PM »

No Mark, but it WILL do it in 3rd according to my speedo and tach at 10,000. You really should ride a good one ;-)

Zaipai · « **Reply #70 on:** December 12, 2015, 09:22:35 PM »

So question (for HM)... For my 550f I was experiencing clutch slip as well. I replaced the stock plates and disc's with Kevlar Disc's and Titanium plates (Barnett Clutch kit) also included stiffer springs and was not all that pricey. I cant get it to slip no matter how hard I try.. Would that be better than using CB750 dics and plates or do the CB750 offer better results and did I waste money on this clutch kit?

Thanks,
.: Scott :.

seanbarney41 · « **Reply #71 on:** December 12, 2015, 10:45:13 PM »

Come on guys...stop over rating the F's...they are barely any better than the k's...if any...especially the F0/f1. F2/3 is a slightly stronger motor, albeit less durable.

Jerry Rxman Griffin aka MuthaF'er · « **Reply #72 on:** December 13, 2015, 10:40:48 AM »

Sean,

Honda was known to up the ante in performance when they came out with a new model then detuning. For sales and bragging perhaps? Mine is engine serial #1954. I recently measured the lobe heights of a K8, F3 and my original cam. Not taking potential wear into account the intakes were all the same which was surprising and interestingly enough my ORIGINAL cam's exhaust lobes were 0.1mm taller than the other 2. I may know how to BS but one thing I don't do is lie so I just stated a question and a fact.

All I can say is my bike was a screaming SOB until I dropped the valve.

Now back to the interesting hybrid 550 experiment........ There was no intent to hijack. Sorry for the distraction.

seanbarney41 · « **Reply #73 on:** December 13, 2015, 11:22:17 AM »

I hear ya Jerry, but I have owned and ridden basically every iteration from K1 to F3, and I have found very little real difference in performance. Sure, every bike is different. It seems some just got put together at the factory with a little more care and thus perform better. I don't doubt you got lucky with a real good running f, but that is not necessarily the norm. On the other hand there are real differences in hardware throughout the models and years, but these manufacturing anomalies seem to randomize the performance possibilities...for example, I had a K6(supposedly the weakest)that was a little better than a K1(going by the hdwre, should have been better) I had. Maybe my K6 got qced real good on a wednsday morning and my K1 got slapped together on friday afternoon? I think the F2/3's are consistently more powerful, but it ends up a wash as they packed on so many extra pounds.

Camrector · « **Reply #74 on:** December 13, 2015, 12:24:21 PM »

Which has absolutely nothing to do with a cb550 motor build. Keep it classy gents.

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Author Topic: Gentleman's Express 550 engine build (Read 40750 times)