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Discussion Starter · #1 ·
Alright, I put this up before and got some good responses so here goes again........

72' Honda 350 twin that runs great accept for anything over 5000 rpm. Only has a hair over 10,000 miles on it.
- Air boxes replaced with stacks
- megaphone exhaust with cherry-bomb style baffles
- Timing and (new) points are spot on, mechanical advance working fine
- valves set to stock spec.
- fuel tank flushed, fuel flow is good

I didn't ride it much before I did anything to it because the tires were junk so I can't say if it did this before the air boxes and exhaust got pulled.

I drilled the jets once, approx. .003 bigger and then it only had a tiny bit of a miss over 5000 rpm. I drilled them again and I'm back to where I started.
Would a stretched timming chain be at fault?? I've heard these were known for this. Or did I go too big on the jets?? This thing is driving me nuts and I'm running out of warm weather. HELP!!!
 

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Moe said:
Alright, I put this up before and got some good responses so here goes again........

72' Honda 350 twin that runs great accept for anything over 5000 rpm. Only has a hair over 10,000 miles on it.
- Air boxes replaced with stacks
- megaphone exhaust with cherry-bomb style baffles
- Timing and (new) points are spot on, mechanical advance working fine
- valves set to stock spec.
- fuel tank flushed, fuel flow is good

I didn't ride it much before I did anything to it because the tires were junk so I can't say if it did this before the air boxes and exhaust got pulled.

I drilled the jets once, approx. .003 bigger and then it only had a tiny bit of a miss over 5000 rpm. I drilled them again and I'm back to where I started.
Would a stretched timming chain be at fault?? I've heard these were known for this. Or did I go too big on the jets?? This thing is driving me nuts and I'm running out of warm weather. HELP!!!
well you really aren't giving enough in the way of actual driveability symptoms for anyone without a crystal ball to have any idea what is wrong....... but stacks and exhaust change will typically mean some carb work... and not limited to making different size holes in the main jets...... which you'll likely find need to be smaller due to reversion associated with straight pipes while finding the needle may need to be raised and/or perhaps fiddle with the air bleed

you can also play with the diaphram springs which you do need to confirm have no pinholes....... easy to do

cv carbs are easy enough to dial in and plenty of non-yost/dynojet gas wasting voodoo type real world tech info out there to be had for free

but you don't say if your bike....... at or below 5K has a soft hestiation, hard bucking hesitation, no indication of what the plugs look like, compression good/bad....... or really much of anything other than it's not running well

I've beaten the piss out of many 350 honda twins and never managed to blow one up nor have I had timing chain problems with any. but I haven't had any really high mileage ones either......... 25K would be tops for me

my last one got 90mpg and I wouldn't mind having it back

they should rev 9 grand no problem and cruise fast enough to leave the average decent 650 Triumph struggling to keep up..... unless the Triumph has been geared very tall and well prepped
 

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Discussion Starter · #3 ·
Well, just for kicks I put the stock air boxes on last night and she runs right up to 9 grand no problem, apparently the stacks I had on there were leaning it out too much over 5000rpm. So now I can actually ride it.......I'll post some pixs after the tank gets painted..........
 
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