370r hybrid motor

[parttime]

have read somewhere and cant remember where about taking a 370 kit and using a +5mm crank with a yz 490 rod and a ktm 370 flat top piston,has anybody tried this setup if so how does it run,dependability and how hard is it to set it up?was just wondering because i picked up a 370 kit and a +5mm crank today and was thinking about trying this setup. any imput would be nice

never heard of that....i wouldnt like having all those different bike parts in my motor, but thats just me, im sure some combination would work though

[deathman53]

I heard about the ktm rod being used being used with a stock crank for kinda stroker, I have heard of the yz490 rod used on a blaster and tri-z, but never a honda.

[parttime]

i wish i could remember where i saw the info at but cant remember for the life of me.they even had a dyno report showing that it was puting out 78hp.pretty impressive for a small motor huh.

[methyman]

I herd of this combination of someone on another web sight talking about it.


Go to the Wiseco Pistons website (wiesco.com) and look under the European bike portion. You will see the KTM 380 pistons. I believe there is one or two years. Once I get the part numbers I just call Wiesco and get them to send me the specs. The biggest piston for the 380 is a 79 mm. It's pretty light as well piston weigh's 249 grams. With the way the pin height is on the KTM piston's have someone build you a 6 mil YZ 490 rod crank. (call Crank Works in Arizona) This combo works well since the KTM pistons have a real low pin height. As far as the sleeves go, I just sent a stock 250R cylinder to Millenium Technologies in Wisconsin to put a big bore aluminum sleeve that will be Nikisil coated.(after porting)(this combo is a 6 mil YZ490 rod, KTM 300 piston 72mm) 79 mm bore x 78 mm stroke will yield approx 382 cc. This is the combo I will build once I get a chance.

[parttime]

thanks for the info. i will start doing some research on that new info that you have shared, thanks alot this is a big help!!!i will probaly start to put one together pretty soon and will share the the results with everyone if they want to know how it does.

[CorvetteZ06]

parttime, let us know about what you find out. this sounds like an amazing setup, and if it puts out close to 80 hp, i will build at least 1 motor with this setup. Thanks man, keep us posted. :cool:

[fiveOnick]

The yz490 rod is very heavy and will vibrate like crazy unless you have it balanced.

[C-LEIGH RACING]

From the YZ465 1980/81 up through the YZ490s to the WR500 in 1991 to 93 all used the same rod.
That rod from Pro-x is a # 04985

Dimentions
23 mm wrist pin hole
31 mm big end hole
137.5 mm eye to eye
20 mm width top & bottom
25mm X 64mm crank pin
25mm X 31 mm X 20mm wide big end crank pin bearing

Stock 250R crank has a 24 mm crank pin & hole & to stroke the crank 6 mms using the 490 rod with a 25 mm pin, would mean machining the crank web holes allmost to the outter edge of the web, got any idea how much that machining & welding would weaken the crank webs themself. That would be the least part about that crank, keeping those crank tins in place would be my worry.
Neil

[parttime]

Originally posted by C-LEIGH RACING
From the YZ465 1980/81 up through the YZ490s to the WR500 in 1991 to 93 all used the same rod.
That rod from Pro-x is a # 04985

Dimentions
23 mm wrist pin hole
31 mm big end hole
137.5 mm eye to eye
20 mm width top & bottom
25mm X 64mm crank pin
25mm X 31 mm X 20mm wide big end crank pin bearing

Stock 250R crank has a 24 mm crank pin & hole & to stroke the crank 6 mms using the 490 rod with a 25 mm pin, would mean machining the crank web holes allmost to the outter edge of the web, got any idea how much that machining & welding would weaken the crank webs themself. That would be the least part about that crank, keeping those crank tins in place would be my worry.
Neil

thanks for the part number and the info Neil.read the same thing about the crank at the same time and that is why they went with a +5mm instead of a 6mm because of the larger pin size

[C-LEIGH RACING]

When you stop & think about it & the problems encountered with a R engine like this, it might be cheaper to just buy a CR500 engine & drop in the frame. If you got to deal with vibs, the 500s not that bad & how its built could stand up to the power your looking.
Aint a lot of vibs in 300-400ft
Neil

[Scott-300ex]

You BOUGHT the kit........................THEN you THOUGHT about it?



















Isn't that backwards?

[parttime]

Originally posted by Scott-300ex
You BOUGHT the kit........................THEN you THOUGHT about it?





















Isn't that backwards?




no its not backwards would have to have the cyl. and crank anyways just need to get the piston, send the crank to crank works and let them insall the 490 rod and build the correct spacer plate. besides when you get a chance to pick up a 370pv cylinder and a +5mm crank for $500.00 you dont think about it twice.

[genoapb]

Originally posted by C-LEIGH RACING
From the YZ465 1980/81 up through the YZ490s to the WR500 in 1991 to 93 all used the same rod.
That rod from Pro-x is a # 04985

Dimentions
23 mm wrist pin hole
31 mm big end hole
137.5 mm eye to eye
20 mm width top & bottom
25mm X 64mm crank pin
25mm X 31 mm X 20mm wide big end crank pin bearing

Stock 250R crank has a 24 mm crank pin & hole & to stroke the crank 6 mms using the 490 rod with a 25 mm pin, would mean machining the crank web holes allmost to the outter edge of the web, got any idea how much that machining & welding would weaken the crank webs themself. That would be the least part about that crank, keeping those crank tins in place would be my worry.
Neil Neil, assuming the dimensions you gave on the yz490 rod are correct. There wont be an issue with the crank being cut too thin. The dimensions on the R rod are very similar and share the same i.d. on the big end of the rods. They are both 31mm. The 1mm difference in the bearings can be made up using the correct bearing sizes. Ive done a bit of research into combos like this and I believe the main reason for them is to add strength, due to the larger piston and strokes which create more stress on certain parts. I doubt there will be any performance increase but reliabilitly should be increased. I use a similar setup on a PSI big bore. The reason behind the odd piston is because it has the pin located higher in the piston so that you dont have to have some extra thick spacer to make up for the longer rod. Another piston option would be a piston from a big bore aftermarket cheetah cylinder. Hope this helps.......

[C-LEIGH RACING]

Alex,
He was talking about a +6 stroke.
Thats the first I've ever heard anything about a +6 stroker, but I guess with machining, anythings possible.

You ever seen a TRX R crank with the tins taken off, those things are thin above the pin hole.
Now a CR250R crank, its alot more beefier around the pin hole & could be machined out farther, but the flywheel side of the crank is to short to use in the TRX bottom end.

Anybody ever built a billet 250R crank.
Neil

[86 Quad R]

i've seen the 490 rod setup being used before on a +4 stroke. infact my engine builder built an R engine using a older CR cylinder but cant remember what piston was used.

i do remember he had problems with the design of the piston. the way the piston was machined at the wrist pin caused exchange of gases across and around the piston at certain locations of the stroke.

out of curiosity, do ya by chance have a pic of the piston that is to be used with the 370 setup?

[duner250r]

Originally posted by parttime
have read somewhere and cant remember where about taking a 370 kit and using a +5mm crank with a yz 490 rod and a ktm 370 flat top piston,has anybody tried this setup if so how does it run,dependability and how hard is it to set it up?was just wondering because i picked up a 370 kit and a +5mm crank today and was thinking about trying this setup. any imput would be nice
THERE IS ONE FOR SALE OVER IN PLANET SAND check it out.

[parttime]

Originally posted by duner250r
THERE IS ONE FOR SALE OVER IN PLANET SAND check it out.


can you post a link to it

[parttime]

found a link to the one i saw here it is http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&ih=011&sspagename=STRK%3AMESE%3AIT&viewitem=&item=320069511111&rd=1,1

[C-LEIGH RACING]

You started doing anything to the engine yet, or still getting parts up.
Neil

[parttime]

got the cylinder and a +5 crank.need to send the crank to crank works so they can install the rod.also going to have them liting it,true and weld,and balance it.then when i get the crank back i will be making a road trip towards nash co. for some fun.i'm now waiting for for my tranny to come back from tyson

[JxxxOxxxE]

did anyone see this...?

Ebay link (http://cgi.ebay.com/ebaymotors/Honda-250R-Big-Bore-motor-polaris-cylinder-Drag-engine_W0QQitemZ170091150734QQcategoryZ43977QQrdZ1 QQcmdZViewItem)

With a polaris cylinder? will a polaris cylinder bolt right to a 250r case?