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Post by Deleted on Aug 10, 2020 16:05:29 GMT 1
So I've decided my carbies will be 28mm mikunis or PWK;s
Exhausts are TSA midrange, a zeel, eventually
Now what else to do withe the barrels which are on plus 1mm but no porting, bridge in inlet is all there
How do i get a bit more grunt out of them, I've no machine shop in my garage and dont know any one in Pertth to contact
Any one any ideas as to what I should do
Cheers
Howard
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Post by jessy03 on Aug 10, 2020 16:26:46 GMT 1
Leave them as they are, add some vforce reeds, that will make a good usable/reliable bike.
Jess
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Post by midlifecrisisrd on Aug 10, 2020 16:46:27 GMT 1
Spend hours with a dremel lol
To be honest I'd give them a little tickle
Not altering the port heights or shapes but take the squareness out of the inlet bridge and take the bottom alloy out to meet the port window in the liner
Then with the exhaust valve open grind out the rear section that hangs down into the port
To be honest as has been said pipes, carbs and reeds will make a big difference
Steve
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Post by veg on Aug 10, 2020 17:01:01 GMT 1
I have somewhere the performance bike articles that tells you how to tune 250 and 350’s now I know it’s dated but it may still be relevant. Only problem is I’ll need to find the magazine.
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Post by JonW on Aug 11, 2020 0:48:30 GMT 1
What reeds you going to run Howard? If youve good pipes to get the exhaust out and good carbs and inlets to get the charge in then the pump (the cylinder) will work well. Especially if the ignition is tuned with a Zeel.
PWK28s, Vforce reeds, Zeel, TSAs, standard airbox (no snorkel), standard inlets will net an upgrade you can feel over stock even with a stock cylinder. If you want to be sure its all good set your squish as well, dont go under 1mm but you'll probably be able to take a leaf out of the head gasket.
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Post by flames on Aug 11, 2020 0:56:03 GMT 1
I have somewhere the performance bike articles that tells you how to tune 250 and 350’s now I know it’s dated but it may still be relevant. Only problem is I’ll need to find the magazine. I believe that article states squish at 0.8-0.9mm......dont listen to it......I did and am hoping when I clean the alloy off the cylinders I don't need to go to the last bore. |
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Post by JonW on Aug 11, 2020 1:04:43 GMT 1
I have somewhere the performance bike articles that tells you how to tune 250 and 350’s now I know it’s dated but it may still be relevant. Only problem is I’ll need to find the magazine. I believe that article states squish at 0.8-0.9mm......dont listen to it......I did and am hoping when I clean the alloy off the cylinders I don't need to go to the last bore. Ahh... sorry to hear that mate. Yes stick to 1-1.1mm to be safe. |
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Post by flames on Aug 11, 2020 1:18:33 GMT 1
I believe that article states squish at 0.8-0.9mm......dont listen to it......I did and am hoping when I clean the alloy off the cylinders I don't need to go to the last bore. Ahh... sorry to hear that mate. Yes stick to 1-1.1mm to be safe. I was planning on fitting some 40mm worktop as a base gasket , just to be on safe side 🤣 |
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Post by Tobyjugs on Aug 11, 2020 10:16:04 GMT 1
Generally the height of the squish is not a problem. It's the compression ratio which is the culprit. I've run engines at 0.80mm without problems. I never read many comments from people who have measured the CR only Squish height.
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Post by flames on Aug 11, 2020 10:41:26 GMT 1
Generally the height of the squish is not a problem. It's the compression ratio which is the culprit. I've run engines at 0.80mm without problems. I never read many comments from people who have measured the CR only Squish height. Guilty as charged. Both times I re built mine I was too caught up in getting the squish where I wanted it and figured if I got that right the rest should fall into place. If barrels were standard it probably wouldn't of been far out but one set are well tuned, the other set is supposedly tuned but nowhere near the same level. I am determined that this time everything is going to be done right and everything measured and calculated to make it right. When I get to that point I will be asking plenty of questions to make sure I get everything tickety boo. |
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Post by reedpete on Aug 11, 2020 10:48:04 GMT 1
1+ for above but to explain a bit I’d say this. A real 0.8 is fine but you need to measure at the narrowest point and also balance the measurement with solder on all Four axis on the piston crown. The piston will rock a little if you just measure in one place. Consequently the 1mm ‘guidance’ is for diy where a Process and measurement safety factor is prudent.
In contrast, un modified volumes on large overbore cylinders with standard (hot) plugs is guaranteed to end in tears...
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Post by JonW on Aug 12, 2020 0:46:02 GMT 1
I agree Peter I think the difference here is 'improving' or 'racing'. If you stick to 1mm+ squish you will be fine. you'll have a more powerful engine than standard. If you race you want every last bit from it, then you should be more scientific about getting every last detail right.
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Post by midlifecrisisrd on Aug 12, 2020 8:49:22 GMT 1
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Post by flames on Aug 12, 2020 11:37:54 GMT 1
Very healthy.
I have always wanted to get more power from mine, tho when I first got her she ran sweet as a nut.....until I decided to re tune ( re: feck it right up ). I have now decided the best way to go is get it running as close to perfect as I can in its current form, then try to extract more if I still feel the need. If I can't get her set up right in the first place there is very little point aiming for more and I won't know what has worked / not worked.
By the time I get her to this point I will be so old and wrinkly I will probably be 'tuning' my Zimmer frame.😁
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