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Post by russie on Jan 17, 2021 15:03:50 GMT 1
I spent half an hour bending Dave at Mutts-Nutts ear the other day so I’m keen on using Serval cylinders to build a 421 engine for my PV. Dave explained the current difficulties he has with his American supplier so I’ll probably buy direct from USA although I’ll also speak to Martin at Mad Biker Designs before I commit to buy. I’d love to hear opinions from those who have gone this route. Dave did say to call again with any questions but I don’t want to waste too much of his time since I can’t buy the stuff from him. I want the bike to have as much midrange as possible as it will be purely for road use and having cranks lasting 500 miles is not what I’ve got in mind. Quite happy to be stripping the motor every now and then for a look though. I’d love to hear from those who have walked this path and get the benefit of your experience. First big questions are:-
1. Thermostat head or not, is it possible with Serval cylinders? Are the stud spacing the same as std Banshee parts, are there domes to suit the 68mm bore size? Which capacity domes are most sensible for road use? I like the idea of controlling the coolant temp as we have plenty cold days up here in the Highlands. I need to decide early on about this as I can buy a head and cylinder kit but BP Racing don’t seem to sell heads with thermostats?
2. Exhausts? I’ll need to get exhausts made to suit Serval cylinder spigots with standard 31K exhaust mount positions. Is Kenny @ TSA still active? I have a pair of his gorgeous exhausts on my 350LC but I’d be just as happy to get exhausts from Dave @ Mutts-Nutts as I’ll be taking it to Dave for set-up once it’s built. Or something else?
3. Carbs. Which carbs will suit me best. I have a spare set of PWKs from a KR1S, should I use these or something else?
4. Oil pump or premix. Can’t really be arsed with premix. Can I get Arrow to increase the delivery rate on my oil pump to work with the 421 build? Oil mixed into the fuel compromises jetting and octane rating too (I think?) Maybe not so much Octane as how it gets into the fuel/oil/air mixture won’t ultimately affect the ratios (Right / wrong?)
5. Air box? Would prefer to run an airbox if possible to reduce intake noise. Is it possible? (KR1S rubbers on std 31K airbox)
6. Ignition. Zeeltronic, Ignitech or something else. Want to use a quick-shifter if possible so that might impact choice but I’m keen to understand the pros & cons of all options.
is that enough for now?
Thanks for all opinions,
Russ.
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Post by headcoats on Jan 17, 2021 16:49:47 GMT 1
What about the 4mm crank in re worked standard YPVS 350 barrels with a custom head , pipes and ignition
If I was to go again , that is what I would do
Few on here done it with mid 70's BHP :-)
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Post by arrow on Jan 17, 2021 17:45:53 GMT 1
Hi Russ, I can sort the pump out for you. It requires six modifications, but let me know ASAP as there is a sixteen week wait for the pumps at the moment.
Note also, that there are certain primary gears that you can run that don't require the uprated pump, but these are expensive.
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Post by russie on Jan 17, 2021 18:13:52 GMT 1
Hi Russ, I can sort the pump out for you. It requires six modifications, but let me know ASAP as there is a sixteen week wait for the pumps at the moment. Note also, that there are certain primary gears that you can run that don't require the uprated pump, but these are expensive. Thanks Gary. I’ve got a spare pump so I’ll get one off to you ASAP. I still have your address somewhere. |
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Post by russie on Jan 17, 2021 18:18:37 GMT 1
What about the 4mm crank in re worked standard YPVS 350 barrels with a custom head , pipes and ignition If I was to go again , that is what I would do Few on here done it with mid 70's BHP :-) I suppose keeping the power valves is one way of ensuring more midrange power. Trouble is, my barrels need rebored, sleeves machined and fitted for the power valve bushes, new bushes and new power valves. My thinking was, by the time I spend the money on all that lot, I could go 421? |
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Post by arrow on Jan 17, 2021 18:32:37 GMT 1
Hi Russ, I can sort the pump out for you. It requires six modifications, but let me know ASAP as there is a sixteen week wait for the pumps at the moment. Note also, that there are certain primary gears that you can run that don't require the uprated pump, but these are expensive. Thanks Gary. I’ve got a spare pump so I’ll get one off to you ASAP. I still have your address somewhere. There is a different procedure these days. Pm sent. |
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Post by Tobyjugs on Jan 17, 2021 19:56:30 GMT 1
What about the 4mm crank in re worked standard YPVS 350 barrels with a custom head , pipes and ignition If I was to go again , that is what I would do Few on here done it with mid 70's BHP :-) I suppose keeping the power valves is one way of ensuring more midrange power. Trouble is, my barrels need rebored, sleeves machined and fitted for the power valve bushes, new bushes and new power valves. My thinking was, by the time I spend the money on all that lot, I could go 421? Hi Russie the 4mm crank is not such a bad idea. I have got a 400cc engine which is standard crank and 68 mm liners. The porting is a bit compromised but it makes 70 PK and has a nice smooth power delivery without any power valves. Pistons are easy to get and i am now on 68.25mm pistons (1st rebore) plenty more left. Once you go the big bore route there are a lot of things that need to be changed. It will cost you a lot more than the two methods above. I believe the YPVS standard gearing is pants and needs to be modified for a longer first and a lower primary gear ratio than 2.65. Your cooling needs to be upgraded big time with a massive radiator probably fans if your going to use it at traffic lights. Would your standard charging system stand up to all the extra load? Thermostat i would say no. If i was to use one i would go with a snow mobile three way unit. This will keep the coolant flowing through the engine. The original on/off thermostat is very old technique. A lot of pipe work has to be changed. Clutch has to be beefed up with the washing machine window and locker (not my cup of tea), stealth locker, heavy springs (only Magilla the gorilla likes this) or do it properly like Yamark with 8 or 9 plate clutch. The list goes on. The very friendly and person i found was Tony Doukas. If he's up for it you can phone him via watts app, but be warned he loves a chat and he can supply just about everything you need. I would only trust pipes made by Mutts or Kenny TSA as these guys have the practical experience. Other people could be just a third party to a pipe maker. |
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Post by midlifecrisisrd on Jan 17, 2021 20:16:18 GMT 1
Untill they make bigger cylinders with power valves again I'll stick to my +4mm 385
Pulls from 2k, plenty midrange and 75-80hp up top safely under 10k revs
Steve
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Post by russie on Jan 17, 2021 22:35:33 GMT 1
Anything north of 70bhp would be fine with me.
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Post by botty on Jan 17, 2021 23:04:42 GMT 1
Untill they make bigger cylinders with power valves again I'll stick to my +4mm 385 Pulls from 2k, plenty midrange and 75-80hp up top safely under 10k revs Steve Same set up as this. 74hp with generic Tdr 350 pipes. So with a proper set of pipes made the the motor. Expect more. |
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Post by midlifecrisisrd on Jan 18, 2021 10:06:32 GMT 1
Anything north of 70bhp would be fine with me. Here's an early dyno run of mine Jetted wrong and no proper ignition curve and hadn't fitted the v4 reeds Certainly not a peaky motor with no bottom or mid Steve  |
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Post by jon on Jan 18, 2021 14:54:32 GMT 1
I’m going the +4 with modified standard YPVS cylinders route.
I too wanted the midrange, but just as importantly a smooth power delivery. Didn’t fancy a large cc motor kicking in the band on a wet day for instance. Lots of fun I should imagine, but tricky to ride on the roads?
Jon
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Post by headcoats on Jan 18, 2021 15:40:57 GMT 1
Whoever takes it on then must do a detailed engine build thread :-)
Will watch with interest
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Post by tsa on Jan 18, 2021 16:41:54 GMT 1
Andy Graham I think it was had 78bhp on a dynapro dyno with a 392 athena and my pipes on. You'd have to ask him what was the rest of the spec though. If I had the choice of cylinders I go for the 421 with the powervalves if they are still available that is.
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Post by midlifecrisisrd on Jan 18, 2021 17:10:31 GMT 1
Andy Graham I think it was had 78bhp on a dynapro dyno with a 392 athena and my pipes on. You'd have to ask him what was the rest of the spec though. If I had the choice of cylinders I go for the 421 with the powervalves if they are still available that is. Don't think you can get them anymore Hence why I don't have them ☹ Steve |
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Post by Tobyjugs on Jan 18, 2021 19:05:28 GMT 1
This dynograph is from a 443, It's not very 2 strokey.. Plenty of mid range and torque and you need a lot of other mods as mentioned above to get the most out of the power it makes. Driveline 443 kit  |
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Post by 123 on Jan 18, 2021 19:21:00 GMT 1
Watching with interest great info
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Post by russie on Jan 18, 2021 20:13:25 GMT 1
Whoever takes it on then must do a detailed engine build thread :-) Will watch with interest I’ll be building it myself. Fully intend to provide you with some entertainment 😉 |
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Post by russie on Jan 18, 2021 20:15:07 GMT 1
Andy Graham I think it was had 78bhp on a dynapro dyno with a 392 athena and my pipes on. You'd have to ask him what was the rest of the spec though. If I had the choice of cylinders I go for the 421 with the powervalves if they are still available that is. Appreciate your input Kenny. I don’t think these cylinders are available? Sounds like the ultimate option for me if they were. Anyone know? |
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Post by jessy03 on Jan 18, 2021 20:49:34 GMT 1
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Post by LC_BOTT on Jan 18, 2021 21:45:12 GMT 1
These Athena barrels kicking out 70 ish HP, are they standard (as bought) or have they all been tweaked/ported? I've got a standard set for mine, as I wanted a base line to see if I needed more, or it was going to give me a nice rideable and therefore reliable bike??
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Post by muttsnuts on Jan 18, 2021 21:55:49 GMT 1
These Athena barrels kicking out 70 ish HP, are they standard (as bought) or have they all been tweaked/ported? I've got a standard set for mine, as I wanted a base line to see if I needed more, or it was going to give me a nice rideable and therefore reliable bike?? with the right setup the stock Athenas with no tweaks etc can do mid 70bhp, done a good few for people who are hitting that, done others for more mid range (different pipe design) and they have done high 60's, low 70's |
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Post by ozzysbikes on Jan 19, 2021 11:55:08 GMT 1
Plus one on going for this kind of build,
I have a spare pair of cylinders so I was thinking of going to + 65.5mm to leave at least one rebore plus a +4mm stroke crank with porting to suit hopefully done by Mick Abbey, I already have a Zeeltronic ignition with pv control, V force 4 reed blocks (not convinced they make a great deal of difference) and Keihin PWK 28,s on my at the moment standard engine, also using Micron pipes because they are period,
Has anyone used and either likes or dislikes Lomas or Jolly Moto pipes ? I have some Lomas pipes for my NS475R and they have a good reputation on the NS
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Post by headcoats on Jan 19, 2021 12:02:36 GMT 1
The Lomas on my Athena 392 only build IMO were the wrong pipes
It flew in the powerband but below that was flat as f**k with a huge flatspot/lull
You really need specialist pipes made for those barrels/tune by Kenny TSA or Mutt Nutts
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Post by midlifecrisisrd on Jan 19, 2021 12:13:08 GMT 1
The likes of Microns and Jolly Moto aren't known for midrange
Its where the likes of Kenny's or Mutts pipes come in as mid and top end boost
The v4 reeds on mine got rid of the torque flat line between 5 and 6k on mine
Steve
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Post by midlifecrisisrd on Jan 19, 2021 12:16:25 GMT 1
Oh and I'd rather have 1mm to play with bore wise so if you are going to throw over a grand at a 385 there is some life in it
The Wiseco 795 pistons (needed to compensate for the 5mm longer rod) only go up in 0.5mm sizes
Steve
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Post by headcoats on Jan 19, 2021 13:02:51 GMT 1
So if you have good barrels will the 795 pistons start at 0.5 or do they have to be 1.00
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Post by Tobyjugs on Jan 19, 2021 13:03:42 GMT 1
The Standard TSA's worked well on the 400cc engine but made to measure pipes made by PS Tuning worked better.
Because of this I have ordered a set of TSA's specifically for a 250cc engine.
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Post by midlifecrisisrd on Jan 19, 2021 13:35:49 GMT 1
So if you have good barrels will the 795 pistons start at 0.5 or do they have to be 1.00 You get 64mm, 64.5mm, 65mm etc If you are have a good bore barrel you will need the clearance checked as the forged pistons run a bigger clearance Steve |
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Post by muttsnuts on Jan 19, 2021 20:17:44 GMT 1
I am just finishing off a 385 engine this week and will be fitting it back in the bike and running it up either later this week, or early next, I'll throw some dyno charts up as its got my latest porting done which has been a bit of a faff to sort, but it should give good results with the pipes I have for it
I've also got a good few dyno charts of 385's in different build/configurations that I've done for people, different porting etc as some people wanted lots of mid range, others wanted all round power, some wanted it leaving as is (stock porting) other than the basic porting needed for a stroker motor
Figures range from 68bhp to 78bhp, of course there is a myriad of exhaust, carbs, ignitions etc combinations in that lot !
PS: before people start asking, I only do porting on engines that I've modified, I don't do "general" porting work
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