Tigcraft project change of direction

[alankelly]

Hi all

Quick question please

Due to size constraints on my Tigcraft project (minimal room to squeeze in a rad) to solve the cooling issue (as want to keep a minimal naked look) thinking of changing the current motor from a liquid cooled engine (YPVS) to a air cooled motor







Yes I know its a different approach (maybe an easier option to solving the rad issue) to solving a problem (and the frame will need some changes to accommodate finned heads etc) But the bike is unique in so many ways already so maybe an air cooled motor adds a twist to the whole build and keeps the minimalIstic look

So my first question to all please is the following

Are rd250 air cooled crank cases similar to RD250LC cases (mounts and overall general size)

Once I know this I no doubt will have other questions and then maybe will be in the market for a aircooled motor if this change is feasible or just cases barrels and heads so I can see what changes are needed and then selling the YPVS motor

Catch up soon and best wishes to all Al

[midlifecrisisrd]

I'm sure all the mounts are different ☹

People put LC top ends on aircooled bottoms so I suppose it mist be possible to put an aircooled top end on an LC bottom

Steve

[midlifecrisisrd]

It's just a pity it wouldn't have the power to fully appreciate that chassis

Steve

[alankelly]

Yes I know but the rad issue is a real headache

I think when you dig into the history of the frame I have I believe it was built for the original owner for super mono racing ( I think with an air cooled single ) hence the lack of space around the engine

And to be honest just want to finish it to a high standard with that naked look and I think an air-cooled motor would look the biz even if the. Chassis outmatches the engine performance

Also harder to get but may try to find a rd400 motor if it looks like this may be an option also?

[alankelly]

Jul 3, 2021 18:01:04 GMT 1 midlifecrisisrd said:

I'm sure all the mounts are different ☹

People put LC top ends on aircooled bottoms so I suppose it mist be possible to put an aircooled top end on an LC bottom

Steve

Well that sounds promising

I wonder if rd400 barrels fit LC cases

Trouble is I don’t know enough about all the different engine types but should be plenty of good advice on here

Best wishes Al

[muttsnuts]

RD400 is 62mm stroke, so no you can't fit 400 barrels on an LC bottom end as its only 54mm stroke.

The LC crank cases should take the 250 air cooled top end though, stud patterns are identical and the stroke is the same and you could use the LC pistons etc, then the only thing to check/adjust would be the port timing if its slightly different

HTH

[midlifecrisisrd]

Nah, +7mm crank in LC cases and 1mm off the bottom of 400 barrels 🤣

Steve

[steve h]

Air cooled? I wonder if anyone has ever used Phazer snowmobile cyls?

R by Ernest Stoppage, on Flickr

[dusty350]

Can you not use 350 aircooled barrels as guys bolt them onto aircooled 250's. I'm no expert on smaller aircooled stuff so maybe not ??
Width of the fins is gonna be an issue with what you have at the mo. You are going to need 11 inches minimum, internally between the subframe down tubes to clear the barrels. Front mount will be in roughly the right place, but the aircooled cases have a much wider casting at the front and use 2 long bolts, but you could just use the 1 top bolt - that's what I did on the Cafe bike. I dont think the mounts will be the issue, more likely the width of the top end. I would post pics but my Flikr account has gone belly up since I changed internet provider on Thursday, but as soon as I recover the account I will post pics of the aircooled mounts. Failing that, look in my build threads as there are lots of pics in there
And, 400 motors are VERY thin on the ground

Dusty

[3tj6]

Can you put 2 rads on the leading edges of the frame, 1 each side like some moto cross bikes do , didn’t the sp1 Honda have rads round the side too?

[alankelly]

Jul 3, 2021 19:41:05 GMT 1 dusty350 said:

Can you not use 350 aircooled barrels as guys bolt them onto aircooled 250's. I'm no expert on smaller aircooled stuff so maybe not ??
Width of the fins is gonna be an issue with what you have at the mo. You are going to need 11 inches minimum, internally between the subframe down tubes to clear the barrels. Front mount will be in roughly the right place, but the aircooled cases have a much wider casting at the front and use 2 long bolts, but you could just use the 1 top bolt - that's what I did on the Cafe bike. I dont think the mounts will be the issue, more likely the width of the top end. I would post pics but my Flikr account has gone belly up since I changed internet provider on Thursday, but as soon as I recover the account I will post pics of the aircooled mounts. Failing that, look in my build threads as there are lots of pics in there
And, 400 motors are VERY thin on the ground

Dusty

Hi Dusty

Just checked frame and I have 9” at the moment so a bit of frame modifications if I source an air cooled twin cylinder motor but much easier than trying to find a rad position

I need to now sit down and do some thinking and then crack on with a possible plan but definitely want to now go the air cooled route with either a twin or large single as some others have suggested


Catch up soon

Best wishes Al

[donkeychomp]

I just might have an RD250 engine...

Alex

[midlifecrisisrd]

Now if you could find an IT490 engine 🍆

Steve

[alankelly]

Yes somebody else mentioned this 😁

Google it and it looks like a single cylinder motor but know nothing about them

Would this be another option??

[midlifecrisisrd]

A single would fit easier

IT490 was only 35hp but it was a torque monster

And aircooled big 80's crosser engine would do

Steve

[midlifecrisisrd]

YZ490 was 55 hp 😱

Steve

[alankelly]

Jul 3, 2021 21:57:13 GMT 1 midlifecrisisrd said:

YZ490 was 55 hp 😱

Steve

Yes had a look and found a couple on the web

Not cheap but it smokes😁

Certainty another option

[alankelly]

Plus single cylinder would make exhaust routing easier too

Like I said earlier I think frame was built by the original owner to race single cylinder, and somebody has pointed out it may have been made to race in the sound of singles racing series in the nineties but never made it into the track so it’s looking more like I may go the single cylinder route but still want to explore if possible if I could fit an air cooled twin first.

At least I have a PV engine to fund the possible motor change😁

Many thanks for all the suggestions and advice so far

Best wishes Al

[reedpete]

Al, If it helped, I have a few aircooled lumps you could use to check fitment and I'm only up the road from you so feel free to come up with tape measure and or borrow stuff.
I’m very familiar with all the twin air cooled motors, and TZR for that matter.
The easiest fix would probably be LC bottom end as the engine mounts are same as YPVS and 350 Aircooled top end as the barrels are narrower and shorter than the 400.

[andy748]

It might be an out there suggestion Al, but a LC Chinese ally rad on the front forks, like an early YZ with a mesh shroud and number board, braided hoses and limited lock stops, never seen it done but we're all a bit crazy enough to try it on this forum??? Andy.

[midlifecrisisrd]

I'd thought that too

If you mount a frame to the headstock like a fairing mount and fit a rad to it so it is fixed

Spray the fins white then black for a number 😀

Steve

[midlifecrisisrd]

Like an oilcooler on the old gsxr street fighters

Steve

[4l04ever]

A 2MA TZR250 engine might be a good option too, as they are smaller and shorter...

[4l04ever]

I think aircooled cylinders would be a lot wider than LC/YPVS due to the fins...

[JonW]

As has been said above, Id look at a rads either side, ie like dirt bikes. Its not a perfect solution, but you only need 750ml of capacity and i think some KTM units will reach that.

As for singles, KTM 380? Im sure some guys raced supermono with something like those motors?

[reedpete]

To get early narrow 350cc AC barrels to work you really need 5mm extra of clearance each side on current setup between that YPVS head and your cradle tubes . The 11” dusty’s talking about would be required for later engines including all 400cc which basically had one extra fin on the head.
No doubt 2MA would be an easier install but I think the end result might seem a bit like reinventing the wheel as both R1Z (trellis frame) and 2MA and 3MA delta box chassis are fairly sorted right out of the box.

[markhoopy]

I think Alan should add the photo of him sat on the bike to this thread just so everyone can see how tiny it is.
The IT465/490 engines are very hard to come by but would certainly be a good option, as would PE400 etc.
How come nobody has suggested a Maico 490 engine yet?

[alankelly]

Ok just so you can see the size of the bike here is a is a picture of me on the project once I got it to a roller




Also I am 5ft 8”

Here is another piccy that shows its size

It funny when you are sat on it it’s really comfy and you feel like you are in it rather than on it if that make sense





Really starting to think large air cooled single here due to frame size ?

Please keep the suggestions coming

Best wishes Al

[muttsnuts]

what about something like a RS/RGV250 engine, they are relatively small, light and can be made to kick out very good power if modified to 300/325cc etc and would probably leave enough room to get a rad fitted

I am assuming the limiting factor here is how far back you can take the motor due to the swinging arm pivot point, which needs to align (give or take) with the front sprocket centre line

A big single would work for sure, but surely that might even mean you have enough space to get a radiator in ?

I have custom radiators made, granted they aren't cheap, but they are made to fit in the space available and have been fitted to ensure sufficent cooling, some are double width/stacked rads, others curved, some split with join pipes, anything is possible within reason, clearly that does cost money though, so is a budget issue as well

[markhoopy]

Jul 4, 2021 11:10:22 GMT 1 alankelly said:

Here is another piccy that shows its size

It funny when you are sat on it it’s really comfy and you feel like you are in it rather than on it if that make sense

Any engine that produces a big amount of power or torque would make that a hard bike to ride.