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gold star DB 350 cams help needed #251929 05/05/09 10:48 am
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rettigj Offline OP
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Hi Gents , first time to the forum , I recently purchased a DB 350 1957 model in clubmans trim the bike is very dead in performance, After being right through the engine I,m now concerned it may have the wrong cams . Currently has 65-2442 inlet and 65-2446 exhaust . after researching it seems these to be 500 clubmans cams or at least the exhaust . the bike is running a standard goldstar muffler .and is not running the advanced pinion gear. Can I please have your thoughts concerning this set up and also any recommendations of cam set up for general club runs . I,m keen on permormance but would like a good starter and smooth runner. there must be some readers out there with well sorted 350,s . Cheers John.
P.S forgot to say running a Concentric

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Re: gold star DB 350 cams help needed [Re: rettigj] #251973 05/05/09 4:15 pm
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Gordo in Comox Online Content
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John: I do not have a "sorted" 350 but it is interesting that the 2446 cam is not listed for the later engine for exhaust. The BB engine lists it but with the 10 degree advance pinion.

Just looking at the chart below I would try a 2450 or the 2491. Interestingly the 2450 uses the 10 degree pinion for the DB but not for the CB when used for scrambles. neither engine uses the 10 degree pinion when the 2450 is used for touring.

One of the Brake test certificates in the BMS book shows the DB32 using 2442/2491 for 29.2 hp at 5500 rpm. The 10 dgree pinion is used for the exhaust.

You could try Phil Pearson for advice if none of the forum lads step up.

Gordo

http://www.pearsongoldstarbsa.freeserve.co.uk/



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Re: gold star DB 350 cams help needed [Re: Gordo in Comox] #252065 05/05/09 9:21 pm
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Dave - NV Offline
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John .. I have two 65-1891 exhaust cams and a 10º advance pinion excess to my needs that I would sell.
but ..
I doubt your low performance is due to your 42/46 cam combo. Those are the cams nearly all of us use in our 500s. You may want to double check your ignition and carb tuning. You are 'spinning' the 'lil girl as needed?


Dave - NV
Re: gold star DB 350 cams help needed [Re: Gordo in Comox] #252165 05/06/09 11:18 am
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rettigj Offline OP
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Thanks Gordo , contacted Phil today via phone and yes we have the wrong cams, hopefully we shall get some life out of it , Thanks for your help.

Regards John

Re: gold star DB 350 cams help needed [Re: Dave - NV] #252166 05/06/09 11:27 am
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Thanks Dave , Bugger just purchased these from Phil , I have been over and over this engine and convinced all is as it should be , what lead me to this was the valve over lap was incorrect . the colour of the plug was as good as we could get it on all rev ranges. Spent many hours jetting etc . shall let you know how we get on Thankyou for your help.

Regards John

Re: gold star DB 350 cams help needed [Re: rettigj] #252218 05/06/09 3:24 pm
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Gordo in Comox Online Content
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John: Interesting. What cams did Phil reccommend for the 350?

It would be interesting to know what cams folks are running in their baby Gold Stars. I suppose the smaller bore with the same stroke would give the engine different characteristics for developing power. The old data (BMS chart) is not too clear on the reasons for the mix and match of cams between the two sizes of engines.

Phil has a chart on his website giving the opening and closing angles and lift of the cams.

Here is a better chart from a Motorcycle Mechanics article.

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Re: gold star DB 350 cams help needed [Re: rettigj] #252226 05/06/09 4:16 pm
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Rich B Offline
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From some information I have:

CB32GS
Inlet Cam Exhaust Cam Pinion
Touring 65-2448 65-2450 65-692 – Std
Scrambles 65-2444 65-1891 65-692 – Std
Racing (petrol) 65-2444 65-1891 65-696 – 10°

DB32GS
Touring 65-2448 65-2450 65-692 – Std
Scrambles 65-2454 65-2450 65-696 – 10°
Clubman’s 65-2442 65-2491 65-692 – Std
Racing 65-2442 65-1891 65-696 – 10°


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Re: gold star DB 350 cams help needed [Re: Rich B] #252339 05/07/09 4:12 am
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Ron - in California R.I.P. Offline
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Well, from what is already said, the cams are not your issue... or..? How do you know it is not running properly..? Have you compared it to another 350..?

And what is the muffler..? Is it a pattern part or original..? Some of the pattern "twitters" are no good...performance wise.

Re: gold star DB 350 cams help needed [Re: Ron - in California R.I.P.] #252559 05/08/09 8:58 am
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I,m really amazed at the response ! , this just comfirms my love of old bikes and the people with in it thanks Guys ! Just to give a back ground on this I have a back ground concerning all things motorcycles , racing many years , and many bike rebuilds . The engine in question has had a total rebuild with all the right gear to clubmans specs and has travelled aprox 100 miles . The engine is very lazey struggling to pull next gear ( std ratios). I have gone over the specs many times and even had a couple people watching over my shoulder to confirm I,m not missing something . We started with the Gp Garb jetted this up then changed over to the Concentric . The Concentric is the best we have and shows good colour on the plug through the range . After talking to Phil he confirmed he has seen this problem before. We even pulled the close ratios out of the box and over to standard.
I know I might be red faced and the end of this but just need to work step by step . I will keep every body up to date on the out come . When riding it feels as if the bike wants more advance and will only start on full advance. We even advanced it up at the maggy but did not improve .The muffler has been a concern ( over baffled ) and have run the bike with it off. and have now opened up the baffling ( small improvment ) . Regards John sorry for the bad spelling

Re: gold star DB 350 cams help needed [Re: rettigj] #252737 05/09/09 3:44 pm
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Ron - in California R.I.P. Offline
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Hi John...

You may find your answer in your last two lines... "It will only start on full advance..."

Your magneto is weak.... a Goldie should start and RUN in with the mag lever slightly retarded.

Also, what spark plug are you using..? Not that the spark plug makes that big a difference short term....

A good Goldie will POP on the first kick...

Ron

Re: gold star DB 350 cams help needed [Re: Ron - in California R.I.P.] #252766 05/09/09 6:37 pm
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John ... Two of the likely suspects causing your issues have been already mentioned seems to me. It would seem to me if the bike runs OK with normal spark plug gap, the mag is reasonably OK.
I would 'lie back' on thinking your 42/46 cams are the problem. It's safe to assume they're installed properly? ..

(1) 'I've heard' of some pattern Twitters being made very restrictive. The OEM and good pattern designs design have a pair of open ended perforated tubes, one is welded into the front cone and the other into the rear setion outlet. the ends of the tubes are offset and do not align inside the muffler. Make semse?

Have you ever wondered why the Twitters look like a mega but aren't? hmmm. Yup you can rebuild a Twitter into a true reverse cone silenced mega with out ward OEM apperance. Let me know if anyone is interested and I'll explain how it's done.

(2) Ignition timing could easily be your problem. I assume you are timing the mag using the 'stick down the hole' method? I also did it this way for many years before going with the SRM/Boyer and it 'kinda sorta works'. Frustrating at best, get ya throwing things at worst!

But, by all means use a timing light for verification. If you haven't done it, we can explain how to set up an accurate degree wheel on a GS calibrated with a bump stop.

Actually the best way to set your timing was devised long ago and is seldom done correctly.
You are aware the bar retard control is 'slack wire' at full advance? And at full retard, with a tight wire, the mag output voltage is lowered? That's why you should only retard about half way for starting.

Timing 'by the book':
Set the bar retard control half way. Now set the engine normal timing using the 'stick in the hole' method. For a stick I've always used lengyhs of 1/8 brass brazing rod marked with a small file.

Now take the bike out onto a good open road where you can run wide open. Using the tach as a reference, diddle the bar retard lever for best top end revs. Insure the carb setting/plug color is OK. The timing giving top speed is the correct timing for the engine. You should be geared to turn at least 7k revs doing this.

Now without touching you final setting of the retard lever, take the bike back to the shop and Accurately measure the timing to this reference, preferrably using a degree wheel and timing light. Now with the retard control to the stop reset the timing to this referenece.
Make sense?

And along these lines ... One of the uses of the GP carb enrichener control was to arrive at the optimum jetting.
BTW, you are aware the normal enrichener operation is with a 'tight wire' on this control? Many of us don't use it and have merely pulled the plunger and capped the cable hole. In other words the plunger is normally pulled up exposing most/all of the slot in the carb body.

By setting the jetting on the lean side with the control set about half way, you can then run top end adjusting for best revs/speed.
You will then have a reference whether to go lean or rich with the jetting. The enrichener controls air to the 'mixing chamber' via the fixed 'emulsion jet' or 'air correction jet'. It's said to simulate going ~ 4 jet sizes richer when the air is restricted.
Make sense?

Tune and Go Fast! That's what Goldies were made for and They love it.


Last edited by dave - NV; 05/09/09 6:39 pm.

Dave - NV
Re: gold star DB 350 cams help needed [Re: Dave - NV] #254012 05/16/09 1:57 am
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rettigj Offline OP
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Ok put the new cams in this morning from Phil 2442 - 2491 with the advance pinion gear , checked all the settings again prior to dismatling and then again putting the new cams in .
And wham oh ! straight up I new it was fixed , took it for a ride and yes pull's like a school boy ! and will tick over with a bit of retard . Thanks to very body for your help , in the coming weeks shall put the GP back on .Regards John


Re: gold star DB 350 cams help needed [Re: rettigj] #254014 05/16/09 2:27 am
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Gordo in Comox Online Content
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John; Sweet! How about a photo of the machine.

Gordo


The roadside repairs make for the best post ride stories.

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