Tuning issues, possible leak? soft seize

Does your Spree/Elite already run great, and you're trying to make it quicker/faster? Need a monster motor swap? Discuss your ideas here.

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Paul604
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Tuning issues, possible leak? soft seize

Post by Paul604 »

so i built this honda tact awhile ago, and it kinda sat for a year or so. Tried to work on tuning it again. 50mm bbk mini stroker crank in a af24 block. 19mm keihin pb carb with a uni filter. Broke it in for a few tank fulls running castrol oil at 32:1 seemed to be running decent. Pilot is at a 42 i think maybe 45 i forget and ive been running with a drilled out main at around a 146ish which was running quite rich. dropped to a 136 then down to a 128 where i soft seized. Still waiting for my cht gauge to come in so all i had was a IR gun, by that point it was reading around 350 but i know thats not very accurate as its gonna cool in the time it takes me to hop off and get a temp. So i let it cool, and was able to ride home, still felt fine. Decided to pull the head and cylinder off just in case. rings feel alright but look to be some markings on them, some markings in the cylinder but nothing i can feel. Will i be fine running it still? ill post some pics. While running the 146 main i had the needle one down from the middle to keep it rich, still seemed to run decent till wot which makes me think i could possibly have a air leak somewhere. Sprayed the engine down with brake clean, no change in rpms or sound. But i did notice an issue. I disabled my oil pump by grinding down the gear on the end cause i didnt have a plug. and it looks like i used the wrong screw to bolt it back on cause it was a little long which didnt allow the pump to be seated all the way in, it had a bit of wiggle to it. Could that have caused an air leak? enough to cause me my tuning issues? It looked like it was sealed but it wasnt tight. Thanks for any help
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1990 Honda Tact
AF24 swap - 50mm bbk, 44mm mini stroker crank, V8 pipe, custom seat cover, 6.9:1 gears
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Mystic
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Re: Tuning issues, possible leak? soft seize

Post by Mystic »

doesnt look too bad, can you catch your fingernail in the scratches to the bore? also did you chamfer the piston skirts and the ports on that bore before you installed it? it doesnt look like the ports were chamfered. yes if the oil pump is not bolted down tight it could cause an airleak
1986 Spree/ Eve af16 swapped 65cc Prodigy vari 8g 9:1 Ruima gears
21mm OKO 42/100 32:1 45mph kymco zx exhaust
1994 Elite S 17.5mm Arreche, Daytona reeds, SEF ramp, pump plugged :D
1987 Elite SE50 af16 swapped
1989 Elite E SB50p
2003 Yamaha Zuma
Paul604
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Re: Tuning issues, possible leak? soft seize

Post by Paul604 »

Can't feel any of the scratches with my nail. Didn't chamfer anything. Kinda new to the whole 2 stroke game so I'll do some searching on that.
1990 Honda Tact
AF24 swap - 50mm bbk, 44mm mini stroker crank, V8 pipe, custom seat cover, 6.9:1 gears
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Bear45-70
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Re: Tuning issues, possible leak? soft seize

Post by Bear45-70 »

Mystic wrote:doesnt look too bad, can you catch your fingernail in the scratches to the bore? also did you chamfer the piston skirts and the ports on that bore before you installed it? it doesnt look like the ports were chamfered. yes if the oil pump is not bolted down tight it could cause an airleak
Doesn't matter if he can catch his finger nail, the piston and rings are junk and when he replaces the piston and rings, he will have to hone it anyway. If he is lucky the bore will hone out, if not a bore job.
Bear 45/70
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Re: Tuning issues, possible leak? soft seize

Post by Mystic »

No offense but Bear must have money coming out his rear he always says buy new stuff :P The 50mm bores have very tight clearance and it is suggested to flex hone the bore before you ever install it which gives the piston and rings a little more clearance and massages the ports. take a small file and get the sharp edges off the ports in the bore and the sharp edges on the piston like at the bottom of the skirts and below where the pin slides in and light hone the cylinder. Make sure the pump is bolted tight and all gasket surfaces are sealed. I know for a fact you can still use a bore and piston after it has seized with a little cleanup as long as the piston isnt melted, deep grooves in the bore or broken rings. I have seized a stock bore with a cheap china piston at least 6 times before i chamfered everything and got it right and it runs strong. btw did you block off the oil lines running to the old pump?
1986 Spree/ Eve af16 swapped 65cc Prodigy vari 8g 9:1 Ruima gears
21mm OKO 42/100 32:1 45mph kymco zx exhaust
1994 Elite S 17.5mm Arreche, Daytona reeds, SEF ramp, pump plugged :D
1987 Elite SE50 af16 swapped
1989 Elite E SB50p
2003 Yamaha Zuma
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Re: Tuning issues, possible leak? soft seize

Post by Bear45-70 »

Mystic wrote:No offense but Bear must have money coming out his rear he always says buy new stuff :PNever said this. It only applies to specific situations and pistons and rings are one of them. The 50mm bores have very tight clearance and it is suggested to flex hone the bore before you ever install it which gives the piston and rings a little more clearance and massages the ports. take a small file Using a file is the amaturish way I've ever heard of for chamfering the port edges. Rookie mistake. and get the sharp edges off the ports in the bore and the sharp edges on the piston like at the bottom of the skirts and below where the pin slides in and light hone the cylinder. Make sure the pump is bolted tight and all gasket surfaces are sealed. I know for a fact you can still use a bore and piston after it has seized with a little cleanup as long as the piston isnt melted, deep grooves in the bore or broken rings.Sure you can. if you want an inefficient motor that leaks. I have seized a stock bore with a cheap china piston at least 6 times before i chamfered everything and got it right and it runs strong.This is an example of someone who has no clue how to do it right. btw did you block off the oil lines running to the old pump?
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'85 Aero 80
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Re: Tuning issues, possible leak? soft seize

Post by veedubh20 »

pb19mm carb lack of fuel feeding to 50mm.

you will need ct chrome intake and 28mm pwk flat slide carb
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