Stuttering issue? '97 VL600C bobber

[jamesbern]

Picking up my bike on Sunday from owner. Bike runs well, idles great, and has good throttle response as well as a positive clutch feel. Bike has an estimated 30k on it. (Speedo is now off the bike since he made it a bobber, probably around 1 1/2 - 2 years ago).

The only issue I saw was a stuttering at WOT while riding quickly. If I gave the throttle a good pull the bike would move fine. The stutter or hesitation only happened on full throttle at speed. I'm thinking coming from street bikes, maybe the revs were too high for that gear? This only happened at full throttle mind you. I could rip through each gear and the bike would respond very quickly. Only if I increased to full throttle while riding at a pretty quick speed would it stutter (maybe hesitate is a better word).

I figured it could be plugs, bad gas, jetting, or air filter. Air filter is one of those velocity stack things. I'm trying to figure out what I need to replace it with a stock-like air filter setup. It has pipes on it, but not sure what kind and I believe it is stock jetting. Pipes still have baffles in it. Cruisers are very new to me so I have a bunch to learn.

Owner said he rides it all the time. Never had any issues with it and it has never left him stranded. From what I saw I would tend to agree. I've never had a bike with this kind of mileage on it before so i'm trying to figure out preventative maintenance for it.

I only have two or three weeks left of riding then it gets stored for the winter.

I plan to change oil, plugs(trying to figure out what kind), check coolant, clean and lube chain, check bolts, tire pressure. I will also be removing the tank in two weeks or so (when riding season is over) and take a look at the carbs. Anything I should look at checking or replacing this winter besides what I already mentioned I was going to?

Carbs as well as V-twins are all new to me. I'm capable of removing wheels, changing coolant and oil, but carbs are new to me as well as fuel and jetting.

I can get a video with my GoPro once I pick up the bike this Sunday.

[jimmywells]

I came from streetbikes too. It's a different world riding on a bobber isn't it?! Anyway, I would put the stock air filter on and see if that helps or put a new set of bigger jets on it. Personally, I would go with the latter of the two considering the bike will run better regardless with a jet kit on it. Not to mention any power increase would be a welcome benefit considering you're used to a bike with more power anyway.

[jamesbern]

I'm trying to scour the web to find the full stock air filter assembly. Seems a bit difficult to find.

[Scrapdog2grand]

Happen in all gears, or just high gear. sure your not hitting the rev limiter?
I would hope its been jetted already, as its got the pipes on it. dont know what kind of intake you have. but a lean main would cause a bog, a rich main will cause a sputter, (it wouldnt nessicarily be at high speed though). see what the plugs look like, sooty would be to rich.

[simpleman77]

What gear are you in when this happens? I'm thinking you might simply be hitting the rev limiter. If it's any gear less than 4th, that is. Tell us what gears this happens in and your shift speeds in those gears.

[jimmywells]

Is there any way you can contact the guy you bought it from? If so, ask him if he had the carbs jetted.

[Scrapdog2grand]

does it seem more severe when the engine is hot, or cold?

[jamesbern]

Originally Posted by Scrapdog2grand

Happen in all gears, or just high gear. sure your not hitting the rev limiter?
I would hope its been jetted already, as its got the pipes on it. dont know what kind of intake you have. but a lean main would cause a bog, a rich main will cause a sputter, (it wouldnt nessicarily be at high speed though). see what the plugs look like, sooty would be to rich.

I'm sort of thinking im hitting the rev limiter, in 2nd or 3rd, but from what I recall I did have it happen in 4th too. I'll pull the plugs when I get the bike.

Originally Posted by simpleman77

What gear are you in when this happens? I'm thinking you might simply be hitting the rev limiter. If it's any gear less than 4th, that is. Tell us what gears this happens in and your shift speeds in those gears.

See above. Not sure of speeds when i'm shifting cause no speedo . I'll toss my GPS on it to get a better idea of what gear and speeds it happens at.

Originally Posted by jimmywells

Is there any way you can contact the guy you bought it from? If so, ask him if he had the carbs jetted.

I texted him asking if he knew. Haven't heard back yet. Bike is still with him currently. Not actually picking it up until Sunday.

[jamesbern]

Originally Posted by Scrapdog2grand

does it seem more severe when the engine is hot, or cold?

I've only ridden ith when the engine was hot. A video may explain it better if I can't figure it out, but I won't have that until at least Tuesday.

I'm pretty sure I was in 4th gear, not sure of the speed, but i'd estimate at around 50mph, pull throttle wide open and I don't gain or really loose speed, just stutter and hesitation. If I let off and then open the throttle again (not all the way mind you) it would ride fine.

If I slow down drop a gear and punch it (just not wide open) it moves out quickly and with authority.

[Scrapdog2grand]

Originally Posted by jamesbern

I've only ridden ith when the engine was hot. A video may explain it better if I can't figure it out, but I won't have that until at least Tuesday.

I'm pretty sure I was in 4th gear, not sure of the speed, but i'd estimate at around 50mph, pull throttle wide open and I don't gain or really loose speed, just stutter and hesitation. If I let off and then open the throttle again (not all the way mind you) it would ride fine.

If I slow down drop a gear and punch it (just not wide open) it moves out quickly and with authority.

I've seen some sites indicate a lean main as a stutter at wide open throttle, to me it feels more like bogging. theres some info out the, take a look at the plugs when you get it. read up on throttle chops for choosing main jets, It'll just give you an idea on plug reading for wide open throttle.
This page indicates leans as a stutter.
How to fine-tune your jetting - Ninja250Wiki
this is one that sells jets, has good ref material on how to tell jet size and manufacturer, and conversion chart for the diff manufactures.
FAQ rejetting 101