'75 suzuki gt250...Buzzing around the block

tom050162

Ride Bmx, Race motorbikes.
Re: '75 suzuki gt250...First start on fuel injection

The amount of work thats gone into this build is just staggering! Look forward to seeing the bike being taken on a ride :)

Tom.
 

joeschuit

Been Around the Block
Re: '75 suzuki gt250...First start on fuel injection

I was able to get some fresh premium and leave the oiling up to the pump. After messing with the mapping and accel enrichments, I ended up with a semi ride-able tune. I haven't plugged the o2 sensor in yet, but that'll be the next step. It literaly starts first kick and settles to an 1800 rpm idle. I'd have the idle lower, but this helps with the charging. The charging system breaks even at 2000rpm, which isn't a problem for normal driving. I think with the current gearing I'll be right around 3000rpm at 45mph in 6th gear. Enjoy this quick video:

http://youtu.be/BePHcg5dNjw

I also finalized some points with the rear fender. It will act only as an inner fender and will not extend past the rear of the frame. I've got about 1/2" of clearance between the tire and the frame with the suspension fully compressed. With the fender just inside the frame, I've got plenty of clearance there. I also found the paint I wanted and tested it on the seat. I'm going to strip the paint and add dual black stripes but at least the color is what I want.



 

haplo_84

Been Around the Block
I'm really anxious to find out about the long term durability of this bike with the switch over to fuel injection. That and also the Mpg difference if any at all because even small 2 strokes were pigs on gas compared to their four stroke brethern.
 

joeschuit

Been Around the Block
When I had the 250 cylinders on the bike completely stock, I was averaging around 38-42 according to the stock gauges. When I bumped it up to the 350 cylinders and larger carbs/chambers it was bumped up to 45mpg. I've heard of low 20's with the kawasaki triples and full race rds. I don't plan on a big increase in mpg, but a definite increase in drivability.
 

two-smoker

I reject your reality, and substitute my own!
The Suzuki two-strokes always were surprisingly efficient...
The bike sounds good Joe! A little stumble right off idle, but picks up revs nicely. Great job!
 

teazer

Over 1,000 Posts
DTT BOTM WINNER
Joe, is that a lean stumble that can be dialled out with a little more injection time or is it related to the slides?

You can try lighter/heavier springs or drill the bleed hole to change responsiveness.
 

joeschuit

Been Around the Block
I haven't spent much time at all dialing in the "jetting". I still need to throw on the o2 sensor and see where I'm at. I have no doubts it'll be much smoother after I get some good weather for tuning.
 

teazer

Over 1,000 Posts
DTT BOTM WINNER
I rigged mine up with data logging O2 sensor, TPS, RPM, CHT now I need the snow and ice to leave so I can ride the thing.

When I did some research as to ideal A:F ratios at different speeds/conditions, the answers were all over the map. Some repeat the old 14.7 and others just say go to around 13:1 for power and 15 for economy.

In reality, the answer is different for each application, but we still need to know what it's doing and then we can plot the answers.
 

MotorbikeBruno

Over 1,000 Posts
I'm just glad I'm lucky enough to watch and learn from both of you gents. Keep up the good work, hope you get some tuning weather soon. I think we've got high 30's on the way here in MN. It would be nice as I think it went below 0 last night :-\
 

biggiesmalls

Been Around the Block
Got here from the BOTM vote and am definitely staying. Sifting through the past couple years of work on this bike is seriously inspiring.
 

joeschuit

Been Around the Block
I told ya I'd get the paint going. I've got some wetsanding and buffing on the gas tank, but this is the look. I ended up doing a wide stripe instead of two. In case someone wants to know, I used a rustoleum base coat and the rustoleum automotive clear coat. The primer was sanded to 600grit with no scratches or pits. Then the base and a coat of clear. The clear was sanded with 1500grit to remove the orangepeel and some slight runs and a second coat of clear on top of that. Second clear was wetsanded with 2000 then 3000grit followed by a buffing with meguiars ultimate compound, then ultimate polish. I'm very happy with the result, by far the best paint job yet.

Concerining the BOTM, I'm very excited to see such enthusiasm over this bike. Sometimes it hard to motivate myself to get the ball rolling, but its worth it to see the replies here. Hopefully it goes over well at the muskegon bike time in july(95% harleys).


 

SONICJK

Reminds me of...me No, I'm sure of it. I hate him
Looks awesome.
PLEASE spray some Spraymax 2k over that. PLEASE.

Its so nice I would hate to see it ruined. Rattle can clear sucks. It wont hold up to anything. You NEED a 2 part clear on a bike.
 

Rich Ard

doin' the backstroke in an estrogen ocean
DTT BOTM WINNER
See you in July, can't wait to check this out in person. Outstanding work.
 

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